[v2,3/3] gstreamer: Generate controls from control_ids_*.yaml files

20903 diff mbox series

This commit implements gstreamer controls for the libcamera element by
generating the controls from the control_ids_*.yaml files using a new
gen-gst-controls.py script. The appropriate meson files are also changed
to automatically run the script when building.

The gen-gst-controls.py script works similar to the gen-controls.py
script by parsing the control_ids_*.yaml files and generating C++ code
for each control.
For the controls to be used as gstreamer properties the type for each
control needs to be translated to the appropriate glib type and a
GEnumValue is generated for each enum control. Then a
g_object_install_property(), _get_property() and _set_property()
function is generated for each control.
The vendor controls get prefixed with "$vendor-" in the final gstreamer
property name.

The C++ code generated by the gen-gst-controls.py script is written into
the template gstlibcamerasrc-controls.cpp.in file. The matching
gstlibcamerasrc-controls.h header defines the GstCameraControls class
which handles the installation of the gstreamer properties as well as
keeping track of the control values and setting and getting the
controls. The content of these functions is generated in the Python
script.

Finally the libcamerasrc element itself is edited to make use of the new
GstCameraControls class. The way this works is by defining a PROP_LAST
enum variant which is passed to the installProperties() function so the
properties are defined with the appropriate offset. When getting or
setting a property PROP_LAST is subtracted from the requested property
to translate the control back into a libcamera::controls:: enum
variant.

Signed-off-by: Jaslo Ziska <jaslo@ziska.de>
---
 src/gstreamer/gstlibcamera-controls.cpp.in | 296 +++++++++++++++++++++
 src/gstreamer/gstlibcamera-controls.h      |  43 +++
 src/gstreamer/gstlibcamerasrc.cpp          |  22 +-
 src/gstreamer/meson.build                  |  10 +
 utils/codegen/controls.py                  |   8 +
 utils/codegen/gen-gst-controls.py          | 151 +++++++++++
 utils/codegen/meson.build                  |   1 +
 7 files changed, 528 insertions(+), 3 deletions(-)
 create mode 100644 src/gstreamer/gstlibcamera-controls.cpp.in
 create mode 100644 src/gstreamer/gstlibcamera-controls.h
 create mode 100755 utils/codegen/gen-gst-controls.py

Hi Jaslo,

Thank you for the patch.

On Tue, Aug 13, 2024 at 02:25:07PM +0200, Jaslo Ziska wrote:
> This commit implements gstreamer controls for the libcamera element by
> generating the controls from the control_ids_*.yaml files using a new
> gen-gst-controls.py script. The appropriate meson files are also changed
> to automatically run the script when building.
> 
> The gen-gst-controls.py script works similar to the gen-controls.py
> script by parsing the control_ids_*.yaml files and generating C++ code
> for each control.
> For the controls to be used as gstreamer properties the type for each
> control needs to be translated to the appropriate glib type and a
> GEnumValue is generated for each enum control. Then a
> g_object_install_property(), _get_property() and _set_property()
> function is generated for each control.
> The vendor controls get prefixed with "$vendor-" in the final gstreamer
> property name.
> 
> The C++ code generated by the gen-gst-controls.py script is written into
> the template gstlibcamerasrc-controls.cpp.in file. The matching
> gstlibcamerasrc-controls.h header defines the GstCameraControls class
> which handles the installation of the gstreamer properties as well as
> keeping track of the control values and setting and getting the
> controls. The content of these functions is generated in the Python
> script.
> 
> Finally the libcamerasrc element itself is edited to make use of the new
> GstCameraControls class. The way this works is by defining a PROP_LAST
> enum variant which is passed to the installProperties() function so the
> properties are defined with the appropriate offset. When getting or
> setting a property PROP_LAST is subtracted from the requested property
> to translate the control back into a libcamera::controls:: enum
> variant.

Looks good to me. I'll focus the review on the parts not related to the
GStreamer internal APIs, and will let Nicolas bring his GStreamer
expertise.

> Signed-off-by: Jaslo Ziska <jaslo@ziska.de>
> ---
>  src/gstreamer/gstlibcamera-controls.cpp.in | 296 +++++++++++++++++++++
>  src/gstreamer/gstlibcamera-controls.h      |  43 +++
>  src/gstreamer/gstlibcamerasrc.cpp          |  22 +-
>  src/gstreamer/meson.build                  |  10 +
>  utils/codegen/controls.py                  |   8 +
>  utils/codegen/gen-gst-controls.py          | 151 +++++++++++
>  utils/codegen/meson.build                  |   1 +
>  7 files changed, 528 insertions(+), 3 deletions(-)
>  create mode 100644 src/gstreamer/gstlibcamera-controls.cpp.in
>  create mode 100644 src/gstreamer/gstlibcamera-controls.h
>  create mode 100755 utils/codegen/gen-gst-controls.py
> 
> diff --git a/src/gstreamer/gstlibcamera-controls.cpp.in b/src/gstreamer/gstlibcamera-controls.cpp.in
> new file mode 100644
> index 00000000..aab7ae24
> --- /dev/null
> +++ b/src/gstreamer/gstlibcamera-controls.cpp.in
> @@ -0,0 +1,296 @@
> +/* SPDX-License-Identifier: LGPL-2.1-or-later */
> +/*
> + * Copyright (C) 2023, Collabora Ltd.
> + *     Author: Nicolas Dufresne <nicolas.dufresne@collabora.com>

I think you can attribute the copyright on this file to yourself.

> + *
> + * GStreamer Camera Controls
> + *
> + * This file is auto-generated. Do not edit.
> + */
> +
> +#include <vector>
> +
> +#include <libcamera/control_ids.h>

And

#include <libcamera/controls.h>
#include <libcamera/geometry.h>

as you use classes defined in those headers below.

> +
> +#include "gstlibcamera-controls.h"
> +
> +using namespace libcamera;
> +
> +{% for vendor, ctrls in controls %}
> +{%- for ctrl in ctrls if ctrl.is_enum %}
> +static const GEnumValue {{ ctrl.name|snake_case }}_types[] = {
> +{%- for enum in ctrl.enum_values %}
> +	{
> +		controls::{{ ctrl.namespace }}{{ enum.name }},
> +		{{ enum.description|format_description|indent('\t\t') }},
> +		"{{ enum.gst_name }}"
> +	},
> +{%- endfor %}
> +	{0, NULL, NULL}
> +};
> +
> +#define TYPE_{{ ctrl.name|snake_case|upper }} \
> +	({{ ctrl.name|snake_case }}_get_type())
> +static GType {{ ctrl.name|snake_case }}_get_type()
> +{
> +	static GType {{ ctrl.name|snake_case }}_type = 0;
> +
> +	if (!{{ ctrl.name|snake_case }}_type)
> +		{{ ctrl.name|snake_case }}_type =
> +			g_enum_register_static("{{ ctrl.name }}",
> +					       {{ ctrl.name|snake_case }}_types);
> +
> +	return {{ ctrl.name|snake_case }}_type;
> +}
> +{% endfor %}
> +{%- endfor %}
> +
> +void GstCameraControls::installProperties(GObjectClass *klass, int lastPropId)
> +{
> +{%- for vendor, ctrls in controls %}
> +{%- for ctrl in ctrls %}
> +
> +{%- set spec %}

I didn't know about set in jinja templates, interesting.

> +{%- if ctrl.is_rectangle -%}
> +gst_param_spec_array(
> +{%- else -%}
> +g_param_spec_{{ ctrl.gtype }}(
> +{%- endif -%}
> +{%- if ctrl.is_array %}
> +	"{{ ctrl.vendor_prefix }}{{ ctrl.name|kebab_case }}-value",
> +	"{{ ctrl.name }} Value",
> +	"One {{ ctrl.name }} element value",
> +{%- else %}
> +	"{{ ctrl.vendor_prefix }}{{ ctrl.name|kebab_case }}",
> +	"{{ ctrl.name }}",
> +	{{ ctrl.description|format_description|indent('\t') }},
> +{%- endif %}
> +{%- if ctrl.is_enum %}
> +	TYPE_{{ ctrl.name|snake_case|upper }},
> +	{{ ctrl.default }},
> +{%- elif ctrl.is_rectangle %}
> +	g_param_spec_int(
> +		"rectangle-value",
> +		"Rectangle Value",
> +		"One rectangle value, either x, y, width or height.",
> +		{{ ctrl.min }}, {{ ctrl.max }}, {{ ctrl.default }},
> +		(GParamFlags) (GST_PARAM_CONTROLLABLE | G_PARAM_READWRITE |
> +			       G_PARAM_STATIC_STRINGS)
> +	),
> +{%- elif ctrl.gtype == 'boolean' %}
> +	{{ ctrl.default }},
> +{%- elif ctrl.gtype in ['float', 'int', 'int64', 'uchar'] %}
> +	{{ ctrl.min }}, {{ ctrl.max }}, {{ ctrl.default }},
> +{%- endif %}
> +	(GParamFlags) (GST_PARAM_CONTROLLABLE | G_PARAM_READWRITE |
> +		       G_PARAM_STATIC_STRINGS)
> +)
> +{%- endset %}
> +
> +	g_object_class_install_property(
> +		klass,
> +		lastPropId + controls::{{ ctrl.namespace }}{{ ctrl.name|snake_case|upper }},
> +{%- if ctrl.is_array %}
> +		gst_param_spec_array(
> +			"{{ ctrl.vendor_prefix }}{{ ctrl.name|kebab_case }}",
> +			"{{ ctrl.name }}",
> +			{{ ctrl.description|format_description|indent('\t\t\t') }},
> +			{{ spec|indent('\t\t\t') }},
> +			(GParamFlags) (GST_PARAM_CONTROLLABLE |
> +				       G_PARAM_READWRITE |
> +				       G_PARAM_STATIC_STRINGS)
> +		)
> +{%- else %}
> +		{{ spec|indent('\t\t') }}
> +{%- endif %}
> +	);
> +{%- endfor %}
> +{%- endfor %}
> +}
> +
> +bool GstCameraControls::getProperty(guint propId, GValue *value,
> +				    [[maybe_unused]] GParamSpec *pspec)
> +{
> +	switch (propId) {
> +{%- for vendor, ctrls in controls %}
> +{%- for ctrl in ctrls %}
> +
> +{%- set value_set %}
> +{%- if ctrl.is_rectangle -%}
> +Point top_left = val.topLeft();
> +Size size = val.size();
> +
> +GValue x = G_VALUE_INIT;
> +g_value_init(&x, G_TYPE_INT);
> +g_value_set_int(&x, top_left.x);
> +gst_value_array_append_and_take_value(&element, &x);
> +
> +GValue y = G_VALUE_INIT;
> +g_value_init(&y, G_TYPE_INT);
> +g_value_set_int(&y, top_left.y);
> +gst_value_array_append_and_take_value(&element, &y);
> +
> +GValue width = G_VALUE_INIT;
> +g_value_init(&width, G_TYPE_INT);
> +g_value_set_int(&width, size.width);
> +gst_value_array_append_and_take_value(&element, &width);
> +
> +GValue height = G_VALUE_INIT;
> +g_value_init(&height, G_TYPE_INT);
> +g_value_set_int(&x, size.height);
> +gst_value_array_append_and_take_value(&element, &height);
> +{%- else -%}
> +g_value_set_{{ ctrl.gtype }}(&element, val);
> +{%- endif -%}
> +{%- endset %}
> +
> +	case controls::{{ ctrl.namespace }}{{ ctrl.name|snake_case|upper }}: {
> +		auto control = metadata_.get(controls::{{ ctrl.namespace }}{{ ctrl.name }});
> +		control = control ? control :
> +			  controls_.get(controls::{{ ctrl.namespace }}{{ ctrl.name }});

		if (!control)
			control = controls_.get(controls::{{ ctrl.namespace }}{{ ctrl.name }});

> +		if (!control) {
> +			GST_WARNING("Control '%s' is not available, default value will be returned",
> +				    controls::{{ ctrl.namespace }}{{ ctrl.name }}.name().c_str());
> +			return true;
> +		}
> +
> +{%- if ctrl.is_array %}
> +		for (size_t i = 0; i < control->size(); ++i) {
> +			GValue element = G_VALUE_INIT;
> +{%- if ctrl.is_rectangle %}
> +			g_value_init(&element, GST_TYPE_PARAM_ARRAY_LIST);
> +{%- else %}
> +			g_value_init(&element, G_TYPE_{{ ctrl.gtype|upper }});
> +{%- endif %}
> +			auto val = (*control)[i];
> +			{{ value_set|indent('\t\t\t\t') }}
> +			gst_value_array_append_and_take_value(value, &element);
> +		}
> +{%- else %}
> +		GValue element = *value;
> +		auto val = *control;
> +		{{ value_set|indent('\t\t\t') }}
> +{%- endif %}
> +
> +		return true;
> +	}
> +{%- endfor %}
> +{%- endfor %}

Add a blank line here as there's one between all the cases above.

> +	default:
> +		return false;
> +	}
> +}
> +
> +bool GstCameraControls::setProperty(guint propId, const GValue *value,
> +				    [[maybe_unused]] GParamSpec *pspec)
> +{
> +	// check whether the camera capabilities are available

Please use C-style comments, start sentences with a capital letter, and
end them with a period.

	/* Check whether the camera capabilities are available. */

> +	if (!capabilities_.empty()) {
> +		// if so, check that the control is supported

		/* If so, check that the control is supported. */

Same below

> +		const ControlId *cid = capabilities_.idmap().at(propId);
> +		auto info = capabilities_.find(cid);
> +
> +		if (info == capabilities_.end()) {
> +			GST_WARNING("Control '%s' is not supported by the camera and will be ignored",
> +				    cid->name().c_str());
> +			return true;
> +		}
> +	}
> +
> +	switch (propId) {
> +{%- for vendor, ctrls in controls %}
> +{%- for ctrl in ctrls %}
> +
> +{%- set value_get %}
> +{%- if ctrl.is_rectangle -%}
> +if (gst_value_array_get_size(element) != 4) {
> +	GST_ERROR("Rectangle must be an array of size 4");

Maybe print the name of the control to make debugging easier ?

> +	return true;
> +}
> +
> +const GValue *r;
> +r = gst_value_array_get_value(element, 0);
> +int x = g_value_get_int(r);
> +r = gst_value_array_get_value(element, 1);
> +int y = g_value_get_int(r);
> +r = gst_value_array_get_value(element, 2);
> +int w = g_value_get_int(r);
> +r = gst_value_array_get_value(element, 3);
> +int h = g_value_get_int(r);
> +
> +auto val = Rectangle(x, y, w, h);

Would it make sense to move all this (including the size check) to a
helper function instead of duplicating the code for each rectangle
control ?

> +{%- else -%}
> +auto val = g_value_get_{{ ctrl.gtype }}(element);
> +{%- endif -%}
> +{%- endset %}
> +
> +	case controls::{{ ctrl.namespace }}{{ ctrl.name|snake_case|upper }}: {
> +{%- if ctrl.is_array %}
> +		size_t size = gst_value_array_get_size(value);
> +{%- if ctrl.size != 0 %}
> +		if (size != {{ ctrl.size }}) {
> +			GST_ERROR("Incorrect array size, must be of size {{ ctrl.size }}");
> +			return true;
> +		}
> +{%- endif %}
> +
> +		std::vector<{{ ctrl.element_type }}> values(size);
> +		for (size_t i = 0; i < size; ++i) {
> +			const GValue *element = gst_value_array_get_value(value, i);
> +			{{ value_get|indent('\t\t\t') }}
> +			values[i] = val;
> +		}
> +		controls_.set(controls::{{ ctrl.namespace }}{{ ctrl.name }},
> +{%- if ctrl.size == 0 %}
> +			      Span<const {{ ctrl.element_type }}>(values.data(), size));
> +{%- else %}
> +			      Span<const {{ ctrl.element_type }}, {{ ctrl.size }}>(values.data(), {{ ctrl.size }}));
> +{%- endif %}
> +{%- else %}
> +		const GValue *element = value;
> +		{{ value_get|indent('\t\t') }}
> +		controls_.set(controls::{{ ctrl.namespace }}{{ ctrl.name }}, val);
> +{%- endif %}
> +		return true;
> +	}
> +{%- endfor %}
> +{%- endfor %}

Add a blank line here too.

> +	default:
> +		return false;
> +	}
> +}
> +
> +void GstCameraControls::setCamera(const std::shared_ptr<libcamera::Camera> &cam)
> +{
> +	capabilities_ = cam->controls();

Is there a need to make a copy of the ControlInfoMap ? Can't we retain a
reference to the camera and use it to access the list of controls ?

> +
> +	// check the controls which were set before the camera capabilities were known
> +	ControlList new_controls;
> +	for (auto control = controls_.begin(); control != controls_.end(); ++control) {

setCamera() is called in gst_libcamera_src_open(). Does that occur
before or after gst_libcamera_src_set_property() ? If it occurs before,
controls_ will be empty here.

> +		unsigned int id = control->first;
> +		ControlValue value = control->second;
> +
> +		const ControlId *cid = capabilities_.idmap().at(id);
> +		auto info = capabilities_.find(cid);
> +
> +		// only add controls which are supported
> +		if (info != capabilities_.end()) {
> +			new_controls.set(id, value);
> +		} else {
> +			GST_WARNING("Control '%s' is not supported by the camera and will be ignored",
> +				    cid->name().c_str());

The control should have been rejected by setProperty() in this case, and
won't end up in controls_ in that case, so I don't think this can occur.

> +		}

You can drop the curly braces.

> +	}
> +
> +	controls_ = new_controls;
> +}
> +
> +void GstCameraControls::applyControls(std::unique_ptr<libcamera::Request> &request)
> +{
> +	request->controls().merge(controls_);

I think you want to clear controls_ here, they don't need to be set in
every request. That's problematic for getControl() though, as it relies
on controls_ accumulating the state of all controls ever set. You'll
probably need two variables, one that accumulates controls, and one that
doesn't.

> +}
> +
> +void GstCameraControls::readMetadata(libcamera::Request *request)
> +{
> +	metadata_ = request->metadata();
> +}

Great handling of white space, the generated code is very readable.

> diff --git a/src/gstreamer/gstlibcamera-controls.h b/src/gstreamer/gstlibcamera-controls.h
> new file mode 100644
> index 00000000..89b616ad
> --- /dev/null
> +++ b/src/gstreamer/gstlibcamera-controls.h
> @@ -0,0 +1,43 @@
> +/* SPDX-License-Identifier: LGPL-2.1-or-later */
> +/*
> + * Copyright (C) 2023, Collabora Ltd.
> + *     Author: Nicolas Dufresne <nicolas.dufresne@collabora.com>
> + *
> + * GStreamer Camera Controls
> + */
> +
> +#pragma once
> +
> +#include <memory>
> +
> +#include <libcamera/camera.h>
> +#include <libcamera/controls.h>
> +#include <libcamera/request.h>
> +
> +#include "gstlibcamerasrc.h"
> +
> +namespace libcamera {
> +
> +class GstCameraControls
> +{
> +public:
> +	static void installProperties(GObjectClass *klass, int lastProp);
> +
> +	bool getProperty(guint propId, GValue *value, GParamSpec *pspec);
> +	bool setProperty(guint propId, const GValue *value, GParamSpec *pspec);
> +
> +	void setCamera(const std::shared_ptr<libcamera::Camera> &cam);
> +
> +	void applyControls(std::unique_ptr<libcamera::Request> &request);
> +	void readMetadata(libcamera::Request *request);
> +
> +private:
> +	/* supported controls and limits of camera */
> +	ControlInfoMap capabilities_;
> +	/* set of user modified controls */
> +	ControlList controls_;
> +	/* metadata returned by the camera */
> +	ControlList metadata_;
> +};
> +
> +} /* namespace libcamera */
> diff --git a/src/gstreamer/gstlibcamerasrc.cpp b/src/gstreamer/gstlibcamerasrc.cpp
> index 40b787c8..8efa25f4 100644
> --- a/src/gstreamer/gstlibcamerasrc.cpp
> +++ b/src/gstreamer/gstlibcamerasrc.cpp
> @@ -37,10 +37,11 @@
>  
>  #include <gst/base/base.h>
>  
> +#include "gstlibcamera-controls.h"
> +#include "gstlibcamera-utils.h"
>  #include "gstlibcameraallocator.h"
>  #include "gstlibcamerapad.h"
>  #include "gstlibcamerapool.h"
> -#include "gstlibcamera-utils.h"
>  
>  using namespace libcamera;
>  
> @@ -128,6 +129,7 @@ struct GstLibcameraSrcState {
>  
>  	ControlList initControls_;
>  	guint group_id_;
> +	GstCameraControls controls_;
>  
>  	int queueRequest();
>  	void requestCompleted(Request *request);
> @@ -153,6 +155,7 @@ struct _GstLibcameraSrc {
>  enum {
>  	PROP_0,
>  	PROP_CAMERA_NAME,
> +	PROP_LAST
>  };
>  
>  static void gst_libcamera_src_child_proxy_init(gpointer g_iface,
> @@ -183,6 +186,9 @@ int GstLibcameraSrcState::queueRequest()
>  	if (!request)
>  		return -ENOMEM;
>  
> +	/* Apply controls */
> +	controls_.applyControls(request);
> +
>  	std::unique_ptr<RequestWrap> wrap =
>  		std::make_unique<RequestWrap>(std::move(request));
>  
> @@ -226,6 +232,9 @@ GstLibcameraSrcState::requestCompleted(Request *request)
>  
>  	{
>  		GLibLocker locker(&lock_);
> +
> +		controls_.readMetadata(request);
> +
>  		wrap = std::move(queuedRequests_.front());
>  		queuedRequests_.pop();
>  	}
> @@ -408,6 +417,8 @@ gst_libcamera_src_open(GstLibcameraSrc *self)
>  		return false;
>  	}
>  
> +	self->state->controls_.setCamera(cam);
> +
>  	cam->requestCompleted.connect(self->state, &GstLibcameraSrcState::requestCompleted);
>  
>  	/* No need to lock here, we didn't start our threads yet. */
> @@ -722,6 +733,7 @@ gst_libcamera_src_set_property(GObject *object, guint prop_id,
>  {
>  	GLibLocker lock(GST_OBJECT(object));
>  	GstLibcameraSrc *self = GST_LIBCAMERA_SRC(object);
> +	GstLibcameraSrcState *state = self->state;
>  
>  	switch (prop_id) {
>  	case PROP_CAMERA_NAME:
> @@ -729,7 +741,8 @@ gst_libcamera_src_set_property(GObject *object, guint prop_id,
>  		self->camera_name = g_value_dup_string(value);
>  		break;
>  	default:
> -		G_OBJECT_WARN_INVALID_PROPERTY_ID(object, prop_id, pspec);
> +		if (!state->controls_.setProperty(prop_id - PROP_LAST, value, pspec))
> +			G_OBJECT_WARN_INVALID_PROPERTY_ID(object, prop_id, pspec);
>  		break;
>  	}
>  }
> @@ -740,13 +753,15 @@ gst_libcamera_src_get_property(GObject *object, guint prop_id, GValue *value,
>  {
>  	GLibLocker lock(GST_OBJECT(object));
>  	GstLibcameraSrc *self = GST_LIBCAMERA_SRC(object);
> +	GstLibcameraSrcState *state = self->state;
>  
>  	switch (prop_id) {
>  	case PROP_CAMERA_NAME:
>  		g_value_set_string(value, self->camera_name);
>  		break;
>  	default:
> -		G_OBJECT_WARN_INVALID_PROPERTY_ID(object, prop_id, pspec);
> +		if (!state->controls_.getProperty(prop_id - PROP_LAST, value, pspec))
> +			G_OBJECT_WARN_INVALID_PROPERTY_ID(object, prop_id, pspec);
>  		break;
>  	}
>  }
> @@ -947,6 +962,7 @@ gst_libcamera_src_class_init(GstLibcameraSrcClass *klass)
>  							     | G_PARAM_STATIC_STRINGS));
>  	g_object_class_install_property(object_class, PROP_CAMERA_NAME, spec);
>  
> +	GstCameraControls::installProperties(object_class, PROP_LAST);
>  }
>  
>  /* GstChildProxy implementation */
> diff --git a/src/gstreamer/meson.build b/src/gstreamer/meson.build
> index c2a01e7b..6b7e53b5 100644
> --- a/src/gstreamer/meson.build
> +++ b/src/gstreamer/meson.build
> @@ -25,6 +25,16 @@ libcamera_gst_sources = [
>      'gstlibcamerasrc.cpp',
>  ]
>  
> +# Generate gstreamer control properties
> +
> +gen_gst_controls_template = files('gstlibcamera-controls.cpp.in')
> +libcamera_gst_sources += custom_target('gstlibcamera-controls.cpp',
> +                                       input : controls_files,
> +                                       output : 'gstlibcamera-controls.cpp',
> +                                       command : [gen_gst_controls, '-o', '@OUTPUT@',
> +                                                  '-t', gen_gst_controls_template, '@INPUT@'],
> +                                       env : py_build_env)
> +
>  libcamera_gst_cpp_args = [
>      '-DVERSION="@0@"'.format(libcamera_git_version),
>      '-DPACKAGE="@0@"'.format(meson.project_name()),
> diff --git a/utils/codegen/controls.py b/utils/codegen/controls.py
> index 7bafee59..03c77cc6 100644
> --- a/utils/codegen/controls.py
> +++ b/utils/codegen/controls.py
> @@ -110,3 +110,11 @@ class Control(object):
>              return f"Span<const {typ}, {self.__size}>"
>          else:
>              return f"Span<const {typ}>"
> +
> +    @property
> +    def element_type(self):
> +        return self.__data.get('type')

I wonder if we shouldn't move the existing type property to
extend_control() in generator scripts, and rename element_type to type.
This can be done on top, you don't have to address it.

> +
> +    @property
> +    def size(self):
> +        return self.__size
> diff --git a/utils/codegen/gen-gst-controls.py b/utils/codegen/gen-gst-controls.py
> new file mode 100755
> index 00000000..5ac8981f
> --- /dev/null
> +++ b/utils/codegen/gen-gst-controls.py
> @@ -0,0 +1,151 @@
> +#!/usr/bin/env python3
> +# SPDX-License-Identifier: GPL-2.0-or-later
> +# Copyright (C) 2019, Google Inc.
> +# Copyright (C) 2024, Jaslo Ziska
> +#
> +# Authors:
> +# Laurent Pinchart <laurent.pinchart@ideasonboard.com>
> +# Jaslo Ziska <jaslo@ziska.de>
> +#
> +# Generate gstreamer control properties from YAML
> +
> +import argparse
> +import jinja2
> +import re
> +import sys
> +import yaml
> +
> +from controls import Control
> +
> +
> +def find_common_prefix(strings):
> +    prefix = strings[0]
> +
> +    for string in strings[1:]:
> +        while string[:len(prefix)] != prefix and prefix:
> +            prefix = prefix[:len(prefix) - 1]
> +        if not prefix:
> +            break
> +
> +    return prefix
> +
> +
> +def format_description(description):
> +    # Substitute doxygen keywords \sa (see also) and \todo
> +    description = re.sub(r'\\sa((?: \w+)+)',
> +                         lambda match: 'See also: ' + ', '.join(
> +                             map(kebab_case, match.group(1).strip().split(' '))
> +                         ) + '.', description)
> +    description = re.sub(r'\\todo', 'Todo:', description)
> +
> +    description = description.strip().split('\n')
> +    return '\n'.join([
> +        '"' + line.replace('\\', r'\\').replace('"', r'\"') + ' "' for line in description if line
> +    ]).rstrip()
> +
> +
> +def snake_case(s):
> +    return ''.join([
> +        c.isupper() and ('_' + c.lower()) or c for c in s
> +    ]).strip('_')
> +
> +
> +def kebab_case(s):
> +    return snake_case(s).replace('_', '-')
> +
> +
> +def extend_control(ctrl):
> +    if ctrl.vendor != 'libcamera':
> +        ctrl.namespace = f'{ctrl.vendor}::'
> +        ctrl.vendor_prefix = f'{ctrl.vendor}-'
> +    else:
> +        ctrl.namespace = ''
> +        ctrl.vendor_prefix = ''
> +
> +    ctrl.is_array = ctrl.size is not None
> +
> +    if ctrl.is_enum:
> +        # remove common prefix from enum variant names

s/# remove/# Remove/

> +        prefix = find_common_prefix([enum.name for enum in ctrl.enum_values])
> +        for enum in ctrl.enum_values:
> +            enum.gst_name = kebab_case(enum.name.removeprefix(prefix))
> +
> +        ctrl.gtype = 'enum'
> +        ctrl.default = '0'
> +    elif ctrl.element_type == 'bool':
> +        ctrl.gtype = 'boolean'
> +        ctrl.default = 'false'
> +    elif ctrl.element_type == 'float':
> +        ctrl.gtype = 'float'
> +        ctrl.default = '0'
> +        ctrl.min = '-G_MAXFLOAT'
> +        ctrl.max = 'G_MAXFLOAT'
> +    elif ctrl.element_type == 'int32_t':
> +        ctrl.gtype = 'int'
> +        ctrl.default = '0'
> +        ctrl.min = 'G_MININT'
> +        ctrl.max = 'G_MAXINT'
> +    elif ctrl.element_type == 'int64_t':
> +        ctrl.gtype = 'int64'
> +        ctrl.default = '0'
> +        ctrl.min = 'G_MININT64'
> +        ctrl.max = 'G_MAXINT64'
> +    elif ctrl.element_type == 'uint8_t':
> +        ctrl.gtype = 'uchar'
> +        ctrl.default = '0'
> +        ctrl.min = '0'
> +        ctrl.max = 'G_MAXUINT8'
> +    elif ctrl.element_type == 'Rectangle':
> +        ctrl.is_rectangle = True
> +        ctrl.default = '0'
> +        ctrl.min = '0'
> +        ctrl.max = 'G_MAXINT'
> +    else:
> +        raise RuntimeError(f'The type `{ctrl.element_type}` is unknown')
> +
> +    return ctrl
> +
> +
> +def main(argv):
> +    # Parse command line arguments
> +    parser = argparse.ArgumentParser()
> +    parser.add_argument('--output', '-o', metavar='file', type=str,
> +                        help='Output file name. Defaults to standard output if not specified.')
> +    parser.add_argument('--template', '-t', dest='template', type=str, required=True,
> +                        help='Template file name.')
> +    parser.add_argument('input', type=str, nargs='+',
> +                        help='Input file name.')
> +
> +    args = parser.parse_args(argv[1:])
> +
> +    controls = {}
> +    for input in args.input:
> +        data = yaml.safe_load(open(input, 'rb').read())
> +
> +        vendor = data['vendor']
> +        ctrls = controls.setdefault(vendor, [])
> +
> +        for ctrl in data['controls']:
> +            ctrl = Control(*ctrl.popitem(), vendor)
> +            ctrls.append(extend_control(ctrl))
> +
> +    data = {'controls': list(controls.items())}
> +
> +    env = jinja2.Environment()
> +    env.filters['format_description'] = format_description
> +    env.filters['snake_case'] = snake_case
> +    env.filters['kebab_case'] = kebab_case
> +    template = env.from_string(open(args.template, 'r', encoding='utf-8').read())
> +    string = template.render(data)
> +
> +    if args.output:
> +        with open(args.output, 'w', encoding='utf-8') as output:
> +            output.write(string)
> +    else:
> +        sys.stdout.write(string)
> +
> +    return 0
> +
> +
> +if __name__ == '__main__':
> +    sys.exit(main(sys.argv))
> diff --git a/utils/codegen/meson.build b/utils/codegen/meson.build
> index adf33bba..904dd66d 100644
> --- a/utils/codegen/meson.build
> +++ b/utils/codegen/meson.build
> @@ -11,6 +11,7 @@ py_modules += ['jinja2', 'yaml']
>  
>  gen_controls = files('gen-controls.py')
>  gen_formats = files('gen-formats.py')
> +gen_gst_controls = files('gen-gst-controls.py')
>  gen_header = files('gen-header.sh')
>  gen_ipa_pub_key = files('gen-ipa-pub-key.py')
>  gen_tracepoints = files('gen-tp-header.py')

Hi Laurent,

thanks for the review.

Laurent Pinchart <laurent.pinchart@ideasonboard.com> writes:
> Hi Jaslo,
>
> Thank you for the patch.
>
> On Tue, Aug 13, 2024 at 02:25:07PM +0200, Jaslo Ziska wrote:
>> This commit implements gstreamer controls for the libcamera 
>> element by
>> generating the controls from the control_ids_*.yaml files using 
>> a new
>> gen-gst-controls.py script. The appropriate meson files are 
>> also changed
>> to automatically run the script when building.
>> 
>> The gen-gst-controls.py script works similar to the 
>> gen-controls.py
>> script by parsing the control_ids_*.yaml files and generating 
>> C++ code
>> for each control.
>> For the controls to be used as gstreamer properties the type 
>> for each
>> control needs to be translated to the appropriate glib type and 
>> a
>> GEnumValue is generated for each enum control. Then a
>> g_object_install_property(), _get_property() and 
>> _set_property()
>> function is generated for each control.
>> The vendor controls get prefixed with "$vendor-" in the final 
>> gstreamer
>> property name.
>> 
>> The C++ code generated by the gen-gst-controls.py script is 
>> written into
>> the template gstlibcamerasrc-controls.cpp.in file. The matching
>> gstlibcamerasrc-controls.h header defines the GstCameraControls 
>> class
>> which handles the installation of the gstreamer properties as 
>> well as
>> keeping track of the control values and setting and getting the
>> controls. The content of these functions is generated in the 
>> Python
>> script.
>> 
>> Finally the libcamerasrc element itself is edited to make use 
>> of the new
>> GstCameraControls class. The way this works is by defining a 
>> PROP_LAST
>> enum variant which is passed to the installProperties() 
>> function so the
>> properties are defined with the appropriate offset. When 
>> getting or
>> setting a property PROP_LAST is subtracted from the requested 
>> property
>> to translate the control back into a libcamera::controls:: enum
>> variant.
>
> Looks good to me. I'll focus the review on the parts not related 
> to the
> GStreamer internal APIs, and will let Nicolas bring his 
> GStreamer
> expertise.
>
>> Signed-off-by: Jaslo Ziska <jaslo@ziska.de>
>> ---
>>  src/gstreamer/gstlibcamera-controls.cpp.in | 296 
>>  +++++++++++++++++++++
>>  src/gstreamer/gstlibcamera-controls.h      |  43 +++
>>  src/gstreamer/gstlibcamerasrc.cpp          |  22 +-
>>  src/gstreamer/meson.build                  |  10 +
>>  utils/codegen/controls.py                  |   8 +
>>  utils/codegen/gen-gst-controls.py          | 151 +++++++++++
>>  utils/codegen/meson.build                  |   1 +
>>  7 files changed, 528 insertions(+), 3 deletions(-)
>>  create mode 100644 src/gstreamer/gstlibcamera-controls.cpp.in
>>  create mode 100644 src/gstreamer/gstlibcamera-controls.h
>>  create mode 100755 utils/codegen/gen-gst-controls.py
>> 
>> diff --git a/src/gstreamer/gstlibcamera-controls.cpp.in 
>> b/src/gstreamer/gstlibcamera-controls.cpp.in
>> new file mode 100644
>> index 00000000..aab7ae24
>> --- /dev/null
>> +++ b/src/gstreamer/gstlibcamera-controls.cpp.in
>> @@ -0,0 +1,296 @@
>> +/* SPDX-License-Identifier: LGPL-2.1-or-later */
>> +/*
>> + * Copyright (C) 2023, Collabora Ltd.
>> + *     Author: Nicolas Dufresne 
>> <nicolas.dufresne@collabora.com>
>
> I think you can attribute the copyright on this file to 
> yourself.
>
>> + *
>> + * GStreamer Camera Controls
>> + *
>> + * This file is auto-generated. Do not edit.
>> + */
>> +
>> +#include <vector>
>> +
>> +#include <libcamera/control_ids.h>
>
> And
>
> #include <libcamera/controls.h>
> #include <libcamera/geometry.h>
>
> as you use classes defined in those headers below.
>
>> +
>> +#include "gstlibcamera-controls.h"
>> +
>> +using namespace libcamera;
>> +
>> +{% for vendor, ctrls in controls %}
>> +{%- for ctrl in ctrls if ctrl.is_enum %}
>> +static const GEnumValue {{ ctrl.name|snake_case }}_types[] = {
>> +{%- for enum in ctrl.enum_values %}
>> +	{
>> +		controls::{{ ctrl.namespace }}{{ enum.name }},
>> +		{{ enum.description|format_description|indent('\t\t') 
>> }},
>> +		"{{ enum.gst_name }}"
>> +	},
>> +{%- endfor %}
>> +	{0, NULL, NULL}
>> +};
>> +
>> +#define TYPE_{{ ctrl.name|snake_case|upper }} \
>> +	({{ ctrl.name|snake_case }}_get_type())
>> +static GType {{ ctrl.name|snake_case }}_get_type()
>> +{
>> +	static GType {{ ctrl.name|snake_case }}_type = 0;
>> +
>> +	if (!{{ ctrl.name|snake_case }}_type)
>> +		{{ ctrl.name|snake_case }}_type =
>> +			g_enum_register_static("{{ ctrl.name }}",
>> +					       {{ ctrl.name|snake_case }}_types);
>> +
>> +	return {{ ctrl.name|snake_case }}_type;
>> +}
>> +{% endfor %}
>> +{%- endfor %}
>> +
>> +void GstCameraControls::installProperties(GObjectClass *klass, 
>> int lastPropId)
>> +{
>> +{%- for vendor, ctrls in controls %}
>> +{%- for ctrl in ctrls %}
>> +
>> +{%- set spec %}
>
> I didn't know about set in jinja templates, interesting.
>
>> +{%- if ctrl.is_rectangle -%}
>> +gst_param_spec_array(
>> +{%- else -%}
>> +g_param_spec_{{ ctrl.gtype }}(
>> +{%- endif -%}
>> +{%- if ctrl.is_array %}
>> +	"{{ ctrl.vendor_prefix }}{{ ctrl.name|kebab_case 
>> }}-value",
>> +	"{{ ctrl.name }} Value",
>> +	"One {{ ctrl.name }} element value",
>> +{%- else %}
>> +	"{{ ctrl.vendor_prefix }}{{ ctrl.name|kebab_case }}",
>> +	"{{ ctrl.name }}",
>> +	{{ ctrl.description|format_description|indent('\t') }},
>> +{%- endif %}
>> +{%- if ctrl.is_enum %}
>> +	TYPE_{{ ctrl.name|snake_case|upper }},
>> +	{{ ctrl.default }},
>> +{%- elif ctrl.is_rectangle %}
>> +	g_param_spec_int(
>> +		"rectangle-value",
>> +		"Rectangle Value",
>> +		"One rectangle value, either x, y, width or height.",
>> +		{{ ctrl.min }}, {{ ctrl.max }}, {{ ctrl.default }},
>> +		(GParamFlags) (GST_PARAM_CONTROLLABLE | 
>> G_PARAM_READWRITE |
>> +			       G_PARAM_STATIC_STRINGS)
>> +	),
>> +{%- elif ctrl.gtype == 'boolean' %}
>> +	{{ ctrl.default }},
>> +{%- elif ctrl.gtype in ['float', 'int', 'int64', 'uchar'] %}
>> +	{{ ctrl.min }}, {{ ctrl.max }}, {{ ctrl.default }},
>> +{%- endif %}
>> +	(GParamFlags) (GST_PARAM_CONTROLLABLE | G_PARAM_READWRITE 
>> |
>> +		       G_PARAM_STATIC_STRINGS)
>> +)
>> +{%- endset %}
>> +
>> +	g_object_class_install_property(
>> +		klass,
>> +		lastPropId + controls::{{ ctrl.namespace }}{{ 
>> ctrl.name|snake_case|upper }},
>> +{%- if ctrl.is_array %}
>> +		gst_param_spec_array(
>> +			"{{ ctrl.vendor_prefix }}{{ ctrl.name|kebab_case 
>> }}",
>> +			"{{ ctrl.name }}",
>> +			{{ 
>> ctrl.description|format_description|indent('\t\t\t') }},
>> +			{{ spec|indent('\t\t\t') }},
>> +			(GParamFlags) (GST_PARAM_CONTROLLABLE |
>> +				       G_PARAM_READWRITE |
>> +				       G_PARAM_STATIC_STRINGS)
>> +		)
>> +{%- else %}
>> +		{{ spec|indent('\t\t') }}
>> +{%- endif %}
>> +	);
>> +{%- endfor %}
>> +{%- endfor %}
>> +}
>> +
>> +bool GstCameraControls::getProperty(guint propId, GValue 
>> *value,
>> +				    [[maybe_unused]] GParamSpec *pspec)
>> +{
>> +	switch (propId) {
>> +{%- for vendor, ctrls in controls %}
>> +{%- for ctrl in ctrls %}
>> +
>> +{%- set value_set %}
>> +{%- if ctrl.is_rectangle -%}
>> +Point top_left = val.topLeft();
>> +Size size = val.size();
>> +
>> +GValue x = G_VALUE_INIT;
>> +g_value_init(&x, G_TYPE_INT);
>> +g_value_set_int(&x, top_left.x);
>> +gst_value_array_append_and_take_value(&element, &x);
>> +
>> +GValue y = G_VALUE_INIT;
>> +g_value_init(&y, G_TYPE_INT);
>> +g_value_set_int(&y, top_left.y);
>> +gst_value_array_append_and_take_value(&element, &y);
>> +
>> +GValue width = G_VALUE_INIT;
>> +g_value_init(&width, G_TYPE_INT);
>> +g_value_set_int(&width, size.width);
>> +gst_value_array_append_and_take_value(&element, &width);
>> +
>> +GValue height = G_VALUE_INIT;
>> +g_value_init(&height, G_TYPE_INT);
>> +g_value_set_int(&x, size.height);
>> +gst_value_array_append_and_take_value(&element, &height);
>> +{%- else -%}
>> +g_value_set_{{ ctrl.gtype }}(&element, val);
>> +{%- endif -%}
>> +{%- endset %}
>> +
>> +	case controls::{{ ctrl.namespace }}{{ 
>> ctrl.name|snake_case|upper }}: {
>> +		auto control = metadata_.get(controls::{{ 
>> ctrl.namespace }}{{ ctrl.name }});
>> +		control = control ? control :
>> +			  controls_.get(controls::{{ ctrl.namespace }}{{ 
>> ctrl.name }});
>
> 		if (!control)
> 			control = controls_.get(controls::{{ ctrl.namespace 
> }}{{ ctrl.name }});
>
>> +		if (!control) {
>> +			GST_WARNING("Control '%s' is not available, 
>> default value will be returned",
>> +				    controls::{{ ctrl.namespace }}{{ ctrl.name 
>> }}.name().c_str());
>> +			return true;
>> +		}
>> +
>> +{%- if ctrl.is_array %}
>> +		for (size_t i = 0; i < control->size(); ++i) {
>> +			GValue element = G_VALUE_INIT;
>> +{%- if ctrl.is_rectangle %}
>> +			g_value_init(&element, GST_TYPE_PARAM_ARRAY_LIST);
>> +{%- else %}
>> +			g_value_init(&element, G_TYPE_{{ ctrl.gtype|upper 
>> }});
>> +{%- endif %}
>> +			auto val = (*control)[i];
>> +			{{ value_set|indent('\t\t\t\t') }}
>> +			gst_value_array_append_and_take_value(value, 
>> &element);
>> +		}
>> +{%- else %}
>> +		GValue element = *value;
>> +		auto val = *control;
>> +		{{ value_set|indent('\t\t\t') }}
>> +{%- endif %}
>> +
>> +		return true;
>> +	}
>> +{%- endfor %}
>> +{%- endfor %}
>
> Add a blank line here as there's one between all the cases 
> above.
>
>> +	default:
>> +		return false;
>> +	}
>> +}
>> +
>> +bool GstCameraControls::setProperty(guint propId, const GValue 
>> *value,
>> +				    [[maybe_unused]] GParamSpec *pspec)
>> +{
>> +	// check whether the camera capabilities are available
>
> Please use C-style comments, start sentences with a capital 
> letter, and
> end them with a period.
>
> 	/* Check whether the camera capabilities are available. */
>
>> +	if (!capabilities_.empty()) {
>> +		// if so, check that the control is supported
>
> 		/* If so, check that the control is supported. */
>
> Same below
>
>> +		const ControlId *cid = 
>> capabilities_.idmap().at(propId);
>> +		auto info = capabilities_.find(cid);
>> +
>> +		if (info == capabilities_.end()) {
>> +			GST_WARNING("Control '%s' is not supported by the 
>> camera and will be ignored",
>> +				    cid->name().c_str());
>> +			return true;
>> +		}
>> +	}
>> +
>> +	switch (propId) {
>> +{%- for vendor, ctrls in controls %}
>> +{%- for ctrl in ctrls %}
>> +
>> +{%- set value_get %}
>> +{%- if ctrl.is_rectangle -%}
>> +if (gst_value_array_get_size(element) != 4) {
>> +	GST_ERROR("Rectangle must be an array of size 4");
>
> Maybe print the name of the control to make debugging easier ?

Good idea, I will add that. It might be a little problematic when 
extracting this part to a separate helper function as the Jinja 
context will then not be available anymore for the name but I will 
try think of something (maybe passing the control name to the 
function?).

>> +	return true;
>> +}
>> +
>> +const GValue *r;
>> +r = gst_value_array_get_value(element, 0);
>> +int x = g_value_get_int(r);
>> +r = gst_value_array_get_value(element, 1);
>> +int y = g_value_get_int(r);
>> +r = gst_value_array_get_value(element, 2);
>> +int w = g_value_get_int(r);
>> +r = gst_value_array_get_value(element, 3);
>> +int h = g_value_get_int(r);
>> +
>> +auto val = Rectangle(x, y, w, h);
>
> Would it make sense to move all this (including the size check) 
> to a
> helper function instead of duplicating the code for each 
> rectangle
> control ?

Good idea, that way I might also be able to drop the Jinja set 
directive and use it directly.

>> +{%- else -%}
>> +auto val = g_value_get_{{ ctrl.gtype }}(element);
>> +{%- endif -%}
>> +{%- endset %}
>> +
>> +	case controls::{{ ctrl.namespace }}{{ 
>> ctrl.name|snake_case|upper }}: {
>> +{%- if ctrl.is_array %}
>> +		size_t size = gst_value_array_get_size(value);
>> +{%- if ctrl.size != 0 %}
>> +		if (size != {{ ctrl.size }}) {
>> +			GST_ERROR("Incorrect array size, must be of size 
>> {{ ctrl.size }}");
>> +			return true;
>> +		}
>> +{%- endif %}
>> +
>> +		std::vector<{{ ctrl.element_type }}> values(size);
>> +		for (size_t i = 0; i < size; ++i) {
>> +			const GValue *element = 
>> gst_value_array_get_value(value, i);
>> +			{{ value_get|indent('\t\t\t') }}
>> +			values[i] = val;
>> +		}
>> +		controls_.set(controls::{{ ctrl.namespace }}{{ 
>> ctrl.name }},
>> +{%- if ctrl.size == 0 %}
>> +			      Span<const {{ ctrl.element_type 
>> }}>(values.data(), size));
>> +{%- else %}
>> +			      Span<const {{ ctrl.element_type }}, {{ 
>> ctrl.size }}>(values.data(), {{ ctrl.size }}));
>> +{%- endif %}
>> +{%- else %}
>> +		const GValue *element = value;
>> +		{{ value_get|indent('\t\t') }}
>> +		controls_.set(controls::{{ ctrl.namespace }}{{ 
>> ctrl.name }}, val);
>> +{%- endif %}
>> +		return true;
>> +	}
>> +{%- endfor %}
>> +{%- endfor %}
>
> Add a blank line here too.
>
>> +	default:
>> +		return false;
>> +	}
>> +}
>> +
>> +void GstCameraControls::setCamera(const 
>> std::shared_ptr<libcamera::Camera> &cam)
>> +{
>> +	capabilities_ = cam->controls();
>
> Is there a need to make a copy of the ControlInfoMap ? Can't we 
> retain a
> reference to the camera and use it to access the list of 
> controls ?

You are right, I could just add a shared_ptr<Camera> member.

>> +
>> +	// check the controls which were set before the camera 
>> capabilities were known
>> +	ControlList new_controls;
>> +	for (auto control = controls_.begin(); control != 
>> controls_.end(); ++control) {
>
> setCamera() is called in gst_libcamera_src_open(). Does that 
> occur
> before or after gst_libcamera_src_set_property() ? If it occurs 
> before,
> controls_ will be empty here.

This is a little complicated, gst_libcamera_src_set_property() can 
be called before and after gst_libcamera_src_open(). So to be able 
to check the controls which were set before the pipeline is 
started I check the controls at this point because the camera 
becomes available here.

>> +		unsigned int id = control->first;
>> +		ControlValue value = control->second;
>> +
>> +		const ControlId *cid = capabilities_.idmap().at(id);
>> +		auto info = capabilities_.find(cid);
>> +
>> +		// only add controls which are supported
>> +		if (info != capabilities_.end()) {
>> +			new_controls.set(id, value);
>> +		} else {
>> +			GST_WARNING("Control '%s' is not supported by the 
>> camera and will be ignored",
>> +				    cid->name().c_str());
>
> The control should have been rejected by setProperty() in this 
> case, and
> won't end up in controls_ in that case, so I don't think this 
> can occur.

Because controls might be set before the camera is available the 
first line in setProperty() checks whether the camera capabilities 
are available and only checks and rejects the controls if they 
are. If the camera was not set when setProperty() is called the 
control gets set unconditionally.

That is why the controls which were set before the camera became 
available are checked at this point when the camera is set.

>> +		}
>
> You can drop the curly braces.
>
>> +	}
>> +
>> +	controls_ = new_controls;
>> +}
>> +
>> +void 
>> GstCameraControls::applyControls(std::unique_ptr<libcamera::Request> 
>> &request)
>> +{
>> +	request->controls().merge(controls_);
>
> I think you want to clear controls_ here, they don't need to be 
> set in
> every request. That's problematic for getControl() though, as it 
> relies
> on controls_ accumulating the state of all controls ever set. 
> You'll
> probably need two variables, one that accumulates controls, and 
> one that
> doesn't.

You are right. I was mistaken about how the libcamera controls 
work, for some reason I thought you had to repeatedly send the 
control with every request. I will change this.

>> +}
>> +
>> +void GstCameraControls::readMetadata(libcamera::Request 
>> *request)
>> +{
>> +	metadata_ = request->metadata();
>> +}
>
> Great handling of white space, the generated code is very 
> readable.
>
>> diff --git a/src/gstreamer/gstlibcamera-controls.h 
>> b/src/gstreamer/gstlibcamera-controls.h
>> new file mode 100644
>> index 00000000..89b616ad
>> --- /dev/null
>> +++ b/src/gstreamer/gstlibcamera-controls.h
>> @@ -0,0 +1,43 @@
>> +/* SPDX-License-Identifier: LGPL-2.1-or-later */
>> +/*
>> + * Copyright (C) 2023, Collabora Ltd.
>> + *     Author: Nicolas Dufresne 
>> <nicolas.dufresne@collabora.com>
>> + *
>> + * GStreamer Camera Controls
>> + */
>> +
>> +#pragma once
>> +
>> +#include <memory>
>> +
>> +#include <libcamera/camera.h>
>> +#include <libcamera/controls.h>
>> +#include <libcamera/request.h>
>> +
>> +#include "gstlibcamerasrc.h"
>> +
>> +namespace libcamera {
>> +
>> +class GstCameraControls
>> +{
>> +public:
>> +	static void installProperties(GObjectClass *klass, int 
>> lastProp);
>> +
>> +	bool getProperty(guint propId, GValue *value, GParamSpec 
>> *pspec);
>> +	bool setProperty(guint propId, const GValue *value, 
>> GParamSpec *pspec);
>> +
>> +	void setCamera(const std::shared_ptr<libcamera::Camera> 
>> &cam);
>> +
>> +	void applyControls(std::unique_ptr<libcamera::Request> 
>> &request);
>> +	void readMetadata(libcamera::Request *request);
>> +
>> +private:
>> +	/* supported controls and limits of camera */
>> +	ControlInfoMap capabilities_;
>> +	/* set of user modified controls */
>> +	ControlList controls_;
>> +	/* metadata returned by the camera */
>> +	ControlList metadata_;
>> +};
>> +
>> +} /* namespace libcamera */
>> diff --git a/src/gstreamer/gstlibcamerasrc.cpp 
>> b/src/gstreamer/gstlibcamerasrc.cpp
>> index 40b787c8..8efa25f4 100644
>> --- a/src/gstreamer/gstlibcamerasrc.cpp
>> +++ b/src/gstreamer/gstlibcamerasrc.cpp
>> @@ -37,10 +37,11 @@
>>  
>>  #include <gst/base/base.h>
>>  
>> +#include "gstlibcamera-controls.h"
>> +#include "gstlibcamera-utils.h"
>>  #include "gstlibcameraallocator.h"
>>  #include "gstlibcamerapad.h"
>>  #include "gstlibcamerapool.h"
>> -#include "gstlibcamera-utils.h"
>>  
>>  using namespace libcamera;
>>  
>> @@ -128,6 +129,7 @@ struct GstLibcameraSrcState {
>>  
>>  	ControlList initControls_;
>>  	guint group_id_;
>> +	GstCameraControls controls_;
>>  
>>  	int queueRequest();
>>  	void requestCompleted(Request *request);
>> @@ -153,6 +155,7 @@ struct _GstLibcameraSrc {
>>  enum {
>>  	PROP_0,
>>  	PROP_CAMERA_NAME,
>> +	PROP_LAST
>>  };
>>  
>>  static void gst_libcamera_src_child_proxy_init(gpointer 
>>  g_iface,
>> @@ -183,6 +186,9 @@ int GstLibcameraSrcState::queueRequest()
>>  	if (!request)
>>  		return -ENOMEM;
>>  
>> +	/* Apply controls */
>> +	controls_.applyControls(request);
>> +
>>  	std::unique_ptr<RequestWrap> wrap =
>>  		std::make_unique<RequestWrap>(std::move(request));
>>  
>> @@ -226,6 +232,9 @@ 
>> GstLibcameraSrcState::requestCompleted(Request *request)
>>  
>>  	{
>>  		GLibLocker locker(&lock_);
>> +
>> +		controls_.readMetadata(request);
>> +
>>  		wrap = std::move(queuedRequests_.front());
>>  		queuedRequests_.pop();
>>  	}
>> @@ -408,6 +417,8 @@ gst_libcamera_src_open(GstLibcameraSrc 
>> *self)
>>  		return false;
>>  	}
>>  
>> +	self->state->controls_.setCamera(cam);
>> +
>>  	cam->requestCompleted.connect(self->state, 
>>  &GstLibcameraSrcState::requestCompleted);
>>  
>>  	/* No need to lock here, we didn't start our threads yet. 
>>  */
>> @@ -722,6 +733,7 @@ gst_libcamera_src_set_property(GObject 
>> *object, guint prop_id,
>>  {
>>  	GLibLocker lock(GST_OBJECT(object));
>>  	GstLibcameraSrc *self = GST_LIBCAMERA_SRC(object);
>> +	GstLibcameraSrcState *state = self->state;
>>  
>>  	switch (prop_id) {
>>  	case PROP_CAMERA_NAME:
>> @@ -729,7 +741,8 @@ gst_libcamera_src_set_property(GObject 
>> *object, guint prop_id,
>>  		self->camera_name = g_value_dup_string(value);
>>  		break;
>>  	default:
>> -		G_OBJECT_WARN_INVALID_PROPERTY_ID(object, prop_id, 
>> pspec);
>> +		if (!state->controls_.setProperty(prop_id - PROP_LAST, 
>> value, pspec))
>> +			G_OBJECT_WARN_INVALID_PROPERTY_ID(object, prop_id, 
>> pspec);
>>  		break;
>>  	}
>>  }
>> @@ -740,13 +753,15 @@ gst_libcamera_src_get_property(GObject 
>> *object, guint prop_id, GValue *value,
>>  {
>>  	GLibLocker lock(GST_OBJECT(object));
>>  	GstLibcameraSrc *self = GST_LIBCAMERA_SRC(object);
>> +	GstLibcameraSrcState *state = self->state;
>>  
>>  	switch (prop_id) {
>>  	case PROP_CAMERA_NAME:
>>  		g_value_set_string(value, self->camera_name);
>>  		break;
>>  	default:
>> -		G_OBJECT_WARN_INVALID_PROPERTY_ID(object, prop_id, 
>> pspec);
>> +		if (!state->controls_.getProperty(prop_id - PROP_LAST, 
>> value, pspec))
>> +			G_OBJECT_WARN_INVALID_PROPERTY_ID(object, prop_id, 
>> pspec);
>>  		break;
>>  	}
>>  }
>> @@ -947,6 +962,7 @@ 
>> gst_libcamera_src_class_init(GstLibcameraSrcClass *klass)
>>  							     | G_PARAM_STATIC_STRINGS));
>>  	g_object_class_install_property(object_class, 
>>  PROP_CAMERA_NAME, spec);
>>  
>> +	GstCameraControls::installProperties(object_class, 
>> PROP_LAST);
>>  }
>>  
>>  /* GstChildProxy implementation */
>> diff --git a/src/gstreamer/meson.build 
>> b/src/gstreamer/meson.build
>> index c2a01e7b..6b7e53b5 100644
>> --- a/src/gstreamer/meson.build
>> +++ b/src/gstreamer/meson.build
>> @@ -25,6 +25,16 @@ libcamera_gst_sources = [
>>      'gstlibcamerasrc.cpp',
>>  ]
>>  
>> +# Generate gstreamer control properties
>> +
>> +gen_gst_controls_template = 
>> files('gstlibcamera-controls.cpp.in')
>> +libcamera_gst_sources += 
>> custom_target('gstlibcamera-controls.cpp',
>> +                                       input : controls_files,
>> +                                       output : 
>> 'gstlibcamera-controls.cpp',
>> +                                       command : 
>> [gen_gst_controls, '-o', '@OUTPUT@',
>> +                                                  '-t', 
>> gen_gst_controls_template, '@INPUT@'],
>> +                                       env : py_build_env)
>> +
>>  libcamera_gst_cpp_args = [
>>      '-DVERSION="@0@"'.format(libcamera_git_version),
>>      '-DPACKAGE="@0@"'.format(meson.project_name()),
>> diff --git a/utils/codegen/controls.py 
>> b/utils/codegen/controls.py
>> index 7bafee59..03c77cc6 100644
>> --- a/utils/codegen/controls.py
>> +++ b/utils/codegen/controls.py
>> @@ -110,3 +110,11 @@ class Control(object):
>>              return f"Span<const {typ}, {self.__size}>"
>>          else:
>>              return f"Span<const {typ}>"
>> +
>> +    @property
>> +    def element_type(self):
>> +        return self.__data.get('type')
>
> I wonder if we shouldn't move the existing type property to
> extend_control() in generator scripts, and rename element_type 
> to type.
> This can be done on top, you don't have to address it.

I'm fine with either, although just calling it type() is a little 
simpler for the gen-gst-controls.py script.

>> +
>> +    @property
>> +    def size(self):
>> +        return self.__size
>> diff --git a/utils/codegen/gen-gst-controls.py 
>> b/utils/codegen/gen-gst-controls.py
>> new file mode 100755
>> index 00000000..5ac8981f
>> --- /dev/null
>> +++ b/utils/codegen/gen-gst-controls.py
>> @@ -0,0 +1,151 @@
>> +#!/usr/bin/env python3
>> +# SPDX-License-Identifier: GPL-2.0-or-later
>> +# Copyright (C) 2019, Google Inc.
>> +# Copyright (C) 2024, Jaslo Ziska
>> +#
>> +# Authors:
>> +# Laurent Pinchart <laurent.pinchart@ideasonboard.com>
>> +# Jaslo Ziska <jaslo@ziska.de>
>> +#
>> +# Generate gstreamer control properties from YAML
>> +
>> +import argparse
>> +import jinja2
>> +import re
>> +import sys
>> +import yaml
>> +
>> +from controls import Control
>> +
>> +
>> +def find_common_prefix(strings):
>> +    prefix = strings[0]
>> +
>> +    for string in strings[1:]:
>> +        while string[:len(prefix)] != prefix and prefix:
>> +            prefix = prefix[:len(prefix) - 1]
>> +        if not prefix:
>> +            break
>> +
>> +    return prefix
>> +
>> +
>> +def format_description(description):
>> +    # Substitute doxygen keywords \sa (see also) and \todo
>> +    description = re.sub(r'\\sa((?: \w+)+)',
>> +                         lambda match: 'See also: ' + ', 
>> '.join(
>> +                             map(kebab_case, 
>> match.group(1).strip().split(' '))
>> +                         ) + '.', description)
>> +    description = re.sub(r'\\todo', 'Todo:', description)
>> +
>> +    description = description.strip().split('\n')
>> +    return '\n'.join([
>> +        '"' + line.replace('\\', r'\\').replace('"', r'\"') + 
>> ' "' for line in description if line
>> +    ]).rstrip()
>> +
>> +
>> +def snake_case(s):
>> +    return ''.join([
>> +        c.isupper() and ('_' + c.lower()) or c for c in s
>> +    ]).strip('_')
>> +
>> +
>> +def kebab_case(s):
>> +    return snake_case(s).replace('_', '-')
>> +
>> +
>> +def extend_control(ctrl):
>> +    if ctrl.vendor != 'libcamera':
>> +        ctrl.namespace = f'{ctrl.vendor}::'
>> +        ctrl.vendor_prefix = f'{ctrl.vendor}-'
>> +    else:
>> +        ctrl.namespace = ''
>> +        ctrl.vendor_prefix = ''
>> +
>> +    ctrl.is_array = ctrl.size is not None
>> +
>> +    if ctrl.is_enum:
>> +        # remove common prefix from enum variant names
>
> s/# remove/# Remove/
>
>> +        prefix = find_common_prefix([enum.name for enum in 
>> ctrl.enum_values])
>> +        for enum in ctrl.enum_values:
>> +            enum.gst_name = 
>> kebab_case(enum.name.removeprefix(prefix))
>> +
>> +        ctrl.gtype = 'enum'
>> +        ctrl.default = '0'
>> +    elif ctrl.element_type == 'bool':
>> +        ctrl.gtype = 'boolean'
>> +        ctrl.default = 'false'
>> +    elif ctrl.element_type == 'float':
>> +        ctrl.gtype = 'float'
>> +        ctrl.default = '0'
>> +        ctrl.min = '-G_MAXFLOAT'
>> +        ctrl.max = 'G_MAXFLOAT'
>> +    elif ctrl.element_type == 'int32_t':
>> +        ctrl.gtype = 'int'
>> +        ctrl.default = '0'
>> +        ctrl.min = 'G_MININT'
>> +        ctrl.max = 'G_MAXINT'
>> +    elif ctrl.element_type == 'int64_t':
>> +        ctrl.gtype = 'int64'
>> +        ctrl.default = '0'
>> +        ctrl.min = 'G_MININT64'
>> +        ctrl.max = 'G_MAXINT64'
>> +    elif ctrl.element_type == 'uint8_t':
>> +        ctrl.gtype = 'uchar'
>> +        ctrl.default = '0'
>> +        ctrl.min = '0'
>> +        ctrl.max = 'G_MAXUINT8'
>> +    elif ctrl.element_type == 'Rectangle':
>> +        ctrl.is_rectangle = True
>> +        ctrl.default = '0'
>> +        ctrl.min = '0'
>> +        ctrl.max = 'G_MAXINT'
>> +    else:
>> +        raise RuntimeError(f'The type `{ctrl.element_type}` is 
>> unknown')
>> +
>> +    return ctrl
>> +
>> +
>> +def main(argv):
>> +    # Parse command line arguments
>> +    parser = argparse.ArgumentParser()
>> +    parser.add_argument('--output', '-o', metavar='file', 
>> type=str,
>> +                        help='Output file name. Defaults to 
>> standard output if not specified.')
>> +    parser.add_argument('--template', '-t', dest='template', 
>> type=str, required=True,
>> +                        help='Template file name.')
>> +    parser.add_argument('input', type=str, nargs='+',
>> +                        help='Input file name.')
>> +
>> +    args = parser.parse_args(argv[1:])
>> +
>> +    controls = {}
>> +    for input in args.input:
>> +        data = yaml.safe_load(open(input, 'rb').read())
>> +
>> +        vendor = data['vendor']
>> +        ctrls = controls.setdefault(vendor, [])
>> +
>> +        for ctrl in data['controls']:
>> +            ctrl = Control(*ctrl.popitem(), vendor)
>> +            ctrls.append(extend_control(ctrl))
>> +
>> +    data = {'controls': list(controls.items())}
>> +
>> +    env = jinja2.Environment()
>> +    env.filters['format_description'] = format_description
>> +    env.filters['snake_case'] = snake_case
>> +    env.filters['kebab_case'] = kebab_case
>> +    template = env.from_string(open(args.template, 'r', 
>> encoding='utf-8').read())
>> +    string = template.render(data)
>> +
>> +    if args.output:
>> +        with open(args.output, 'w', encoding='utf-8') as 
>> output:
>> +            output.write(string)
>> +    else:
>> +        sys.stdout.write(string)
>> +
>> +    return 0
>> +
>> +
>> +if __name__ == '__main__':
>> +    sys.exit(main(sys.argv))
>> diff --git a/utils/codegen/meson.build 
>> b/utils/codegen/meson.build
>> index adf33bba..904dd66d 100644
>> --- a/utils/codegen/meson.build
>> +++ b/utils/codegen/meson.build
>> @@ -11,6 +11,7 @@ py_modules += ['jinja2', 'yaml']
>>  
>>  gen_controls = files('gen-controls.py')
>>  gen_formats = files('gen-formats.py')
>> +gen_gst_controls = files('gen-gst-controls.py')
>>  gen_header = files('gen-header.sh')
>>  gen_ipa_pub_key = files('gen-ipa-pub-key.py')
>>  gen_tracepoints = files('gen-tp-header.py')

Best regards

Jaslo

On Tue, Aug 27, 2024 at 01:49:49PM +0200, Jaslo Ziska wrote:
> Laurent Pinchart writes:
> > On Tue, Aug 13, 2024 at 02:25:07PM +0200, Jaslo Ziska wrote:
> >> This commit implements gstreamer controls for the libcamera element by
> >> generating the controls from the control_ids_*.yaml files using a new
> >> gen-gst-controls.py script. The appropriate meson files are also changed
> >> to automatically run the script when building.
> >> 
> >> The gen-gst-controls.py script works similar to the gen-controls.py
> >> script by parsing the control_ids_*.yaml files and generating C++ code
> >> for each control.
> >> For the controls to be used as gstreamer properties the type for each
> >> control needs to be translated to the appropriate glib type and a
> >> GEnumValue is generated for each enum control. Then a
> >> g_object_install_property(), _get_property() and _set_property()
> >> function is generated for each control.
> >> The vendor controls get prefixed with "$vendor-" in the final gstreamer
> >> property name.
> >> 
> >> The C++ code generated by the gen-gst-controls.py script is written into
> >> the template gstlibcamerasrc-controls.cpp.in file. The matching
> >> gstlibcamerasrc-controls.h header defines the GstCameraControls class
> >> which handles the installation of the gstreamer properties as well as
> >> keeping track of the control values and setting and getting the
> >> controls. The content of these functions is generated in the Python
> >> script.
> >> 
> >> Finally the libcamerasrc element itself is edited to make use of the new
> >> GstCameraControls class. The way this works is by defining a PROP_LAST
> >> enum variant which is passed to the installProperties() function so the
> >> properties are defined with the appropriate offset. When getting or
> >> setting a property PROP_LAST is subtracted from the requested property
> >> to translate the control back into a libcamera::controls:: enum variant.
> >
> > Looks good to me. I'll focus the review on the parts not related to the
> > GStreamer internal APIs, and will let Nicolas bring his GStreamer
> > expertise.
> >
> >> Signed-off-by: Jaslo Ziska <jaslo@ziska.de>
> >> ---
> >>  src/gstreamer/gstlibcamera-controls.cpp.in | 296 +++++++++++++++++++++
> >>  src/gstreamer/gstlibcamera-controls.h      |  43 +++
> >>  src/gstreamer/gstlibcamerasrc.cpp          |  22 +-
> >>  src/gstreamer/meson.build                  |  10 +
> >>  utils/codegen/controls.py                  |   8 +
> >>  utils/codegen/gen-gst-controls.py          | 151 +++++++++++
> >>  utils/codegen/meson.build                  |   1 +
> >>  7 files changed, 528 insertions(+), 3 deletions(-)
> >>  create mode 100644 src/gstreamer/gstlibcamera-controls.cpp.in
> >>  create mode 100644 src/gstreamer/gstlibcamera-controls.h
> >>  create mode 100755 utils/codegen/gen-gst-controls.py
> >> 
> >> diff --git a/src/gstreamer/gstlibcamera-controls.cpp.in 
> >> b/src/gstreamer/gstlibcamera-controls.cpp.in
> >> new file mode 100644
> >> index 00000000..aab7ae24
> >> --- /dev/null
> >> +++ b/src/gstreamer/gstlibcamera-controls.cpp.in
> >> @@ -0,0 +1,296 @@
> >> +/* SPDX-License-Identifier: LGPL-2.1-or-later */
> >> +/*
> >> + * Copyright (C) 2023, Collabora Ltd.
> >> + *     Author: Nicolas Dufresne <nicolas.dufresne@collabora.com>
> >
> > I think you can attribute the copyright on this file to 
> > yourself.
> >
> >> + *
> >> + * GStreamer Camera Controls
> >> + *
> >> + * This file is auto-generated. Do not edit.
> >> + */
> >> +
> >> +#include <vector>
> >> +
> >> +#include <libcamera/control_ids.h>
> >
> > And
> >
> > #include <libcamera/controls.h>
> > #include <libcamera/geometry.h>
> >
> > as you use classes defined in those headers below.
> >
> >> +
> >> +#include "gstlibcamera-controls.h"
> >> +
> >> +using namespace libcamera;
> >> +
> >> +{% for vendor, ctrls in controls %}
> >> +{%- for ctrl in ctrls if ctrl.is_enum %}
> >> +static const GEnumValue {{ ctrl.name|snake_case }}_types[] = {
> >> +{%- for enum in ctrl.enum_values %}
> >> +	{
> >> +		controls::{{ ctrl.namespace }}{{ enum.name }},
> >> +		{{ enum.description|format_description|indent('\t\t') 
> >> }},
> >> +		"{{ enum.gst_name }}"
> >> +	},
> >> +{%- endfor %}
> >> +	{0, NULL, NULL}
> >> +};
> >> +
> >> +#define TYPE_{{ ctrl.name|snake_case|upper }} \
> >> +	({{ ctrl.name|snake_case }}_get_type())
> >> +static GType {{ ctrl.name|snake_case }}_get_type()
> >> +{
> >> +	static GType {{ ctrl.name|snake_case }}_type = 0;
> >> +
> >> +	if (!{{ ctrl.name|snake_case }}_type)
> >> +		{{ ctrl.name|snake_case }}_type =
> >> +			g_enum_register_static("{{ ctrl.name }}",
> >> +					       {{ ctrl.name|snake_case }}_types);
> >> +
> >> +	return {{ ctrl.name|snake_case }}_type;
> >> +}
> >> +{% endfor %}
> >> +{%- endfor %}
> >> +
> >> +void GstCameraControls::installProperties(GObjectClass *klass, 
> >> int lastPropId)
> >> +{
> >> +{%- for vendor, ctrls in controls %}
> >> +{%- for ctrl in ctrls %}
> >> +
> >> +{%- set spec %}
> >
> > I didn't know about set in jinja templates, interesting.
> >
> >> +{%- if ctrl.is_rectangle -%}
> >> +gst_param_spec_array(
> >> +{%- else -%}
> >> +g_param_spec_{{ ctrl.gtype }}(
> >> +{%- endif -%}
> >> +{%- if ctrl.is_array %}
> >> +	"{{ ctrl.vendor_prefix }}{{ ctrl.name|kebab_case 
> >> }}-value",
> >> +	"{{ ctrl.name }} Value",
> >> +	"One {{ ctrl.name }} element value",
> >> +{%- else %}
> >> +	"{{ ctrl.vendor_prefix }}{{ ctrl.name|kebab_case }}",
> >> +	"{{ ctrl.name }}",
> >> +	{{ ctrl.description|format_description|indent('\t') }},
> >> +{%- endif %}
> >> +{%- if ctrl.is_enum %}
> >> +	TYPE_{{ ctrl.name|snake_case|upper }},
> >> +	{{ ctrl.default }},
> >> +{%- elif ctrl.is_rectangle %}
> >> +	g_param_spec_int(
> >> +		"rectangle-value",
> >> +		"Rectangle Value",
> >> +		"One rectangle value, either x, y, width or height.",
> >> +		{{ ctrl.min }}, {{ ctrl.max }}, {{ ctrl.default }},
> >> +		(GParamFlags) (GST_PARAM_CONTROLLABLE | 
> >> G_PARAM_READWRITE |
> >> +			       G_PARAM_STATIC_STRINGS)
> >> +	),
> >> +{%- elif ctrl.gtype == 'boolean' %}
> >> +	{{ ctrl.default }},
> >> +{%- elif ctrl.gtype in ['float', 'int', 'int64', 'uchar'] %}
> >> +	{{ ctrl.min }}, {{ ctrl.max }}, {{ ctrl.default }},
> >> +{%- endif %}
> >> +	(GParamFlags) (GST_PARAM_CONTROLLABLE | G_PARAM_READWRITE 
> >> |
> >> +		       G_PARAM_STATIC_STRINGS)
> >> +)
> >> +{%- endset %}
> >> +
> >> +	g_object_class_install_property(
> >> +		klass,
> >> +		lastPropId + controls::{{ ctrl.namespace }}{{ 
> >> ctrl.name|snake_case|upper }},
> >> +{%- if ctrl.is_array %}
> >> +		gst_param_spec_array(
> >> +			"{{ ctrl.vendor_prefix }}{{ ctrl.name|kebab_case 
> >> }}",
> >> +			"{{ ctrl.name }}",
> >> +			{{ 
> >> ctrl.description|format_description|indent('\t\t\t') }},
> >> +			{{ spec|indent('\t\t\t') }},
> >> +			(GParamFlags) (GST_PARAM_CONTROLLABLE |
> >> +				       G_PARAM_READWRITE |
> >> +				       G_PARAM_STATIC_STRINGS)
> >> +		)
> >> +{%- else %}
> >> +		{{ spec|indent('\t\t') }}
> >> +{%- endif %}
> >> +	);
> >> +{%- endfor %}
> >> +{%- endfor %}
> >> +}
> >> +
> >> +bool GstCameraControls::getProperty(guint propId, GValue 
> >> *value,
> >> +				    [[maybe_unused]] GParamSpec *pspec)
> >> +{
> >> +	switch (propId) {
> >> +{%- for vendor, ctrls in controls %}
> >> +{%- for ctrl in ctrls %}
> >> +
> >> +{%- set value_set %}
> >> +{%- if ctrl.is_rectangle -%}
> >> +Point top_left = val.topLeft();
> >> +Size size = val.size();
> >> +
> >> +GValue x = G_VALUE_INIT;
> >> +g_value_init(&x, G_TYPE_INT);
> >> +g_value_set_int(&x, top_left.x);
> >> +gst_value_array_append_and_take_value(&element, &x);
> >> +
> >> +GValue y = G_VALUE_INIT;
> >> +g_value_init(&y, G_TYPE_INT);
> >> +g_value_set_int(&y, top_left.y);
> >> +gst_value_array_append_and_take_value(&element, &y);
> >> +
> >> +GValue width = G_VALUE_INIT;
> >> +g_value_init(&width, G_TYPE_INT);
> >> +g_value_set_int(&width, size.width);
> >> +gst_value_array_append_and_take_value(&element, &width);
> >> +
> >> +GValue height = G_VALUE_INIT;
> >> +g_value_init(&height, G_TYPE_INT);
> >> +g_value_set_int(&x, size.height);
> >> +gst_value_array_append_and_take_value(&element, &height);
> >> +{%- else -%}
> >> +g_value_set_{{ ctrl.gtype }}(&element, val);
> >> +{%- endif -%}
> >> +{%- endset %}
> >> +
> >> +	case controls::{{ ctrl.namespace }}{{ 
> >> ctrl.name|snake_case|upper }}: {
> >> +		auto control = metadata_.get(controls::{{ 
> >> ctrl.namespace }}{{ ctrl.name }});
> >> +		control = control ? control :
> >> +			  controls_.get(controls::{{ ctrl.namespace }}{{ 
> >> ctrl.name }});
> >
> > 		if (!control)
> > 			control = controls_.get(controls::{{ ctrl.namespace 
> > }}{{ ctrl.name }});
> >
> >> +		if (!control) {
> >> +			GST_WARNING("Control '%s' is not available, 
> >> default value will be returned",
> >> +				    controls::{{ ctrl.namespace }}{{ ctrl.name 
> >> }}.name().c_str());
> >> +			return true;
> >> +		}
> >> +
> >> +{%- if ctrl.is_array %}
> >> +		for (size_t i = 0; i < control->size(); ++i) {
> >> +			GValue element = G_VALUE_INIT;
> >> +{%- if ctrl.is_rectangle %}
> >> +			g_value_init(&element, GST_TYPE_PARAM_ARRAY_LIST);
> >> +{%- else %}
> >> +			g_value_init(&element, G_TYPE_{{ ctrl.gtype|upper 
> >> }});
> >> +{%- endif %}
> >> +			auto val = (*control)[i];
> >> +			{{ value_set|indent('\t\t\t\t') }}
> >> +			gst_value_array_append_and_take_value(value, 
> >> &element);
> >> +		}
> >> +{%- else %}
> >> +		GValue element = *value;
> >> +		auto val = *control;
> >> +		{{ value_set|indent('\t\t\t') }}
> >> +{%- endif %}
> >> +
> >> +		return true;
> >> +	}
> >> +{%- endfor %}
> >> +{%- endfor %}
> >
> > Add a blank line here as there's one between all the cases 
> > above.
> >
> >> +	default:
> >> +		return false;
> >> +	}
> >> +}
> >> +
> >> +bool GstCameraControls::setProperty(guint propId, const GValue 
> >> *value,
> >> +				    [[maybe_unused]] GParamSpec *pspec)
> >> +{
> >> +	// check whether the camera capabilities are available
> >
> > Please use C-style comments, start sentences with a capital 
> > letter, and
> > end them with a period.
> >
> > 	/* Check whether the camera capabilities are available. */
> >
> >> +	if (!capabilities_.empty()) {
> >> +		// if so, check that the control is supported
> >
> > 		/* If so, check that the control is supported. */
> >
> > Same below
> >
> >> +		const ControlId *cid = 
> >> capabilities_.idmap().at(propId);
> >> +		auto info = capabilities_.find(cid);
> >> +
> >> +		if (info == capabilities_.end()) {
> >> +			GST_WARNING("Control '%s' is not supported by the 
> >> camera and will be ignored",
> >> +				    cid->name().c_str());
> >> +			return true;
> >> +		}
> >> +	}
> >> +
> >> +	switch (propId) {
> >> +{%- for vendor, ctrls in controls %}
> >> +{%- for ctrl in ctrls %}
> >> +
> >> +{%- set value_get %}
> >> +{%- if ctrl.is_rectangle -%}
> >> +if (gst_value_array_get_size(element) != 4) {
> >> +	GST_ERROR("Rectangle must be an array of size 4");
> >
> > Maybe print the name of the control to make debugging easier ?
> 
> Good idea, I will add that. It might be a little problematic when 
> extracting this part to a separate helper function as the Jinja 
> context will then not be available anymore for the name but I will 
> try think of something (maybe passing the control name to the 
> function?).

Yes, passing the control name to the function seems fine.
 
> >> +	return true;
> >> +}
> >> +
> >> +const GValue *r;
> >> +r = gst_value_array_get_value(element, 0);
> >> +int x = g_value_get_int(r);
> >> +r = gst_value_array_get_value(element, 1);
> >> +int y = g_value_get_int(r);
> >> +r = gst_value_array_get_value(element, 2);
> >> +int w = g_value_get_int(r);
> >> +r = gst_value_array_get_value(element, 3);
> >> +int h = g_value_get_int(r);
> >> +
> >> +auto val = Rectangle(x, y, w, h);
> >
> > Would it make sense to move all this (including the size check) to a
> > helper function instead of duplicating the code for each rectangle
> > control ?
> 
> Good idea, that way I might also be able to drop the Jinja set 
> directive and use it directly.
> 
> >> +{%- else -%}
> >> +auto val = g_value_get_{{ ctrl.gtype }}(element);
> >> +{%- endif -%}
> >> +{%- endset %}
> >> +
> >> +	case controls::{{ ctrl.namespace }}{{ 
> >> ctrl.name|snake_case|upper }}: {
> >> +{%- if ctrl.is_array %}
> >> +		size_t size = gst_value_array_get_size(value);
> >> +{%- if ctrl.size != 0 %}
> >> +		if (size != {{ ctrl.size }}) {
> >> +			GST_ERROR("Incorrect array size, must be of size 
> >> {{ ctrl.size }}");
> >> +			return true;
> >> +		}
> >> +{%- endif %}
> >> +
> >> +		std::vector<{{ ctrl.element_type }}> values(size);
> >> +		for (size_t i = 0; i < size; ++i) {
> >> +			const GValue *element = 
> >> gst_value_array_get_value(value, i);
> >> +			{{ value_get|indent('\t\t\t') }}
> >> +			values[i] = val;
> >> +		}
> >> +		controls_.set(controls::{{ ctrl.namespace }}{{ 
> >> ctrl.name }},
> >> +{%- if ctrl.size == 0 %}
> >> +			      Span<const {{ ctrl.element_type 
> >> }}>(values.data(), size));
> >> +{%- else %}
> >> +			      Span<const {{ ctrl.element_type }}, {{ 
> >> ctrl.size }}>(values.data(), {{ ctrl.size }}));
> >> +{%- endif %}
> >> +{%- else %}
> >> +		const GValue *element = value;
> >> +		{{ value_get|indent('\t\t') }}
> >> +		controls_.set(controls::{{ ctrl.namespace }}{{ 
> >> ctrl.name }}, val);
> >> +{%- endif %}
> >> +		return true;
> >> +	}
> >> +{%- endfor %}
> >> +{%- endfor %}
> >
> > Add a blank line here too.
> >
> >> +	default:
> >> +		return false;
> >> +	}
> >> +}
> >> +
> >> +void GstCameraControls::setCamera(const 
> >> std::shared_ptr<libcamera::Camera> &cam)
> >> +{
> >> +	capabilities_ = cam->controls();
> >
> > Is there a need to make a copy of the ControlInfoMap ? Can't we 
> > retain a
> > reference to the camera and use it to access the list of 
> > controls ?
> 
> You are right, I could just add a shared_ptr<Camera> member.
> 
> >> +
> >> +	// check the controls which were set before the camera 
> >> capabilities were known
> >> +	ControlList new_controls;
> >> +	for (auto control = controls_.begin(); control != 
> >> controls_.end(); ++control) {
> >
> > setCamera() is called in gst_libcamera_src_open(). Does that occur
> > before or after gst_libcamera_src_set_property() ? If it occurs before,
> > controls_ will be empty here.
> 
> This is a little complicated, gst_libcamera_src_set_property() can 
> be called before and after gst_libcamera_src_open(). So to be able 
> to check the controls which were set before the pipeline is 
> started I check the controls at this point because the camera 
> becomes available here.

Maybe a comment would be useful to explain this.

> >> +		unsigned int id = control->first;
> >> +		ControlValue value = control->second;
> >> +
> >> +		const ControlId *cid = capabilities_.idmap().at(id);
> >> +		auto info = capabilities_.find(cid);
> >> +
> >> +		// only add controls which are supported
> >> +		if (info != capabilities_.end()) {
> >> +			new_controls.set(id, value);
> >> +		} else {
> >> +			GST_WARNING("Control '%s' is not supported by the camera and will be ignored",
> >> +				    cid->name().c_str());
> >
> > The control should have been rejected by setProperty() in this case, and
> > won't end up in controls_ in that case, so I don't think this can occur.
> 
> Because controls might be set before the camera is available the 
> first line in setProperty() checks whether the camera capabilities 
> are available and only checks and rejects the controls if they 
> are. If the camera was not set when setProperty() is called the 
> control gets set unconditionally.
> 
> That is why the controls which were set before the camera became 
> available are checked at this point when the camera is set.

I see. I suppose there's no way to simplify this and requires the camera
to be set before controls are set ?

> >> +		}
> >
> > You can drop the curly braces.
> >
> >> +	}
> >> +
> >> +	controls_ = new_controls;
> >> +}
> >> +
> >> +void 
> >> GstCameraControls::applyControls(std::unique_ptr<libcamera::Request> 
> >> &request)
> >> +{
> >> +	request->controls().merge(controls_);
> >
> > I think you want to clear controls_ here, they don't need to be set in
> > every request. That's problematic for getControl() though, as it relies
> > on controls_ accumulating the state of all controls ever set. You'll
> > probably need two variables, one that accumulates controls, and one that
> > doesn't.
> 
> You are right. I was mistaken about how the libcamera controls 
> work, for some reason I thought you had to repeatedly send the 
> control with every request. I will change this.
> 
> >> +}
> >> +
> >> +void GstCameraControls::readMetadata(libcamera::Request 
> >> *request)
> >> +{
> >> +	metadata_ = request->metadata();
> >> +}
> >
> > Great handling of white space, the generated code is very 
> > readable.
> >
> >> diff --git a/src/gstreamer/gstlibcamera-controls.h 
> >> b/src/gstreamer/gstlibcamera-controls.h
> >> new file mode 100644
> >> index 00000000..89b616ad
> >> --- /dev/null
> >> +++ b/src/gstreamer/gstlibcamera-controls.h
> >> @@ -0,0 +1,43 @@
> >> +/* SPDX-License-Identifier: LGPL-2.1-or-later */
> >> +/*
> >> + * Copyright (C) 2023, Collabora Ltd.
> >> + *     Author: Nicolas Dufresne <nicolas.dufresne@collabora.com>
> >> + *
> >> + * GStreamer Camera Controls
> >> + */
> >> +
> >> +#pragma once
> >> +
> >> +#include <memory>
> >> +
> >> +#include <libcamera/camera.h>
> >> +#include <libcamera/controls.h>
> >> +#include <libcamera/request.h>
> >> +
> >> +#include "gstlibcamerasrc.h"
> >> +
> >> +namespace libcamera {
> >> +
> >> +class GstCameraControls
> >> +{
> >> +public:
> >> +	static void installProperties(GObjectClass *klass, int lastProp);
> >> +
> >> +	bool getProperty(guint propId, GValue *value, GParamSpec *pspec);
> >> +	bool setProperty(guint propId, const GValue *value, GParamSpec *pspec);
> >> +
> >> +	void setCamera(const std::shared_ptr<libcamera::Camera> &cam);
> >> +
> >> +	void applyControls(std::unique_ptr<libcamera::Request> &request);
> >> +	void readMetadata(libcamera::Request *request);
> >> +
> >> +private:
> >> +	/* supported controls and limits of camera */
> >> +	ControlInfoMap capabilities_;
> >> +	/* set of user modified controls */
> >> +	ControlList controls_;
> >> +	/* metadata returned by the camera */
> >> +	ControlList metadata_;
> >> +};
> >> +
> >> +} /* namespace libcamera */
> >> diff --git a/src/gstreamer/gstlibcamerasrc.cpp 
> >> b/src/gstreamer/gstlibcamerasrc.cpp
> >> index 40b787c8..8efa25f4 100644
> >> --- a/src/gstreamer/gstlibcamerasrc.cpp
> >> +++ b/src/gstreamer/gstlibcamerasrc.cpp
> >> @@ -37,10 +37,11 @@
> >>  
> >>  #include <gst/base/base.h>
> >>  
> >> +#include "gstlibcamera-controls.h"
> >> +#include "gstlibcamera-utils.h"
> >>  #include "gstlibcameraallocator.h"
> >>  #include "gstlibcamerapad.h"
> >>  #include "gstlibcamerapool.h"
> >> -#include "gstlibcamera-utils.h"
> >>  
> >>  using namespace libcamera;
> >>  
> >> @@ -128,6 +129,7 @@ struct GstLibcameraSrcState {
> >>  
> >>  	ControlList initControls_;
> >>  	guint group_id_;
> >> +	GstCameraControls controls_;
> >>  
> >>  	int queueRequest();
> >>  	void requestCompleted(Request *request);
> >> @@ -153,6 +155,7 @@ struct _GstLibcameraSrc {
> >>  enum {
> >>  	PROP_0,
> >>  	PROP_CAMERA_NAME,
> >> +	PROP_LAST
> >>  };
> >>  
> >>  static void gst_libcamera_src_child_proxy_init(gpointer g_iface,
> >> @@ -183,6 +186,9 @@ int GstLibcameraSrcState::queueRequest()
> >>  	if (!request)
> >>  		return -ENOMEM;
> >>  
> >> +	/* Apply controls */
> >> +	controls_.applyControls(request);
> >> +
> >>  	std::unique_ptr<RequestWrap> wrap =
> >>  		std::make_unique<RequestWrap>(std::move(request));
> >>  
> >> @@ -226,6 +232,9 @@ 
> >> GstLibcameraSrcState::requestCompleted(Request *request)
> >>  
> >>  	{
> >>  		GLibLocker locker(&lock_);
> >> +
> >> +		controls_.readMetadata(request);
> >> +
> >>  		wrap = std::move(queuedRequests_.front());
> >>  		queuedRequests_.pop();
> >>  	}
> >> @@ -408,6 +417,8 @@ gst_libcamera_src_open(GstLibcameraSrc *self)
> >>  		return false;
> >>  	}
> >>  
> >> +	self->state->controls_.setCamera(cam);
> >> +
> >>  	cam->requestCompleted.connect(self->state, 
> >>  &GstLibcameraSrcState::requestCompleted);
> >>  
> >>  	/* No need to lock here, we didn't start our threads yet. 
> >>  */
> >> @@ -722,6 +733,7 @@ gst_libcamera_src_set_property(GObject 
> >> *object, guint prop_id,
> >>  {
> >>  	GLibLocker lock(GST_OBJECT(object));
> >>  	GstLibcameraSrc *self = GST_LIBCAMERA_SRC(object);
> >> +	GstLibcameraSrcState *state = self->state;
> >>  
> >>  	switch (prop_id) {
> >>  	case PROP_CAMERA_NAME:
> >> @@ -729,7 +741,8 @@ gst_libcamera_src_set_property(GObject *object, guint prop_id,
> >>  		self->camera_name = g_value_dup_string(value);
> >>  		break;
> >>  	default:
> >> -		G_OBJECT_WARN_INVALID_PROPERTY_ID(object, prop_id, pspec);
> >> +		if (!state->controls_.setProperty(prop_id - PROP_LAST, value, pspec))
> >> +			G_OBJECT_WARN_INVALID_PROPERTY_ID(object, prop_id, pspec);
> >>  		break;
> >>  	}
> >>  }
> >> @@ -740,13 +753,15 @@ gst_libcamera_src_get_property(GObject 
> >> *object, guint prop_id, GValue *value,
> >>  {
> >>  	GLibLocker lock(GST_OBJECT(object));
> >>  	GstLibcameraSrc *self = GST_LIBCAMERA_SRC(object);
> >> +	GstLibcameraSrcState *state = self->state;
> >>  
> >>  	switch (prop_id) {
> >>  	case PROP_CAMERA_NAME:
> >>  		g_value_set_string(value, self->camera_name);
> >>  		break;
> >>  	default:
> >> -		G_OBJECT_WARN_INVALID_PROPERTY_ID(object, prop_id, pspec);
> >> +		if (!state->controls_.getProperty(prop_id - PROP_LAST, value, pspec))
> >> +			G_OBJECT_WARN_INVALID_PROPERTY_ID(object, prop_id, pspec);
> >>  		break;
> >>  	}
> >>  }
> >> @@ -947,6 +962,7 @@ 
> >> gst_libcamera_src_class_init(GstLibcameraSrcClass *klass)
> >>  							     | G_PARAM_STATIC_STRINGS));
> >>  	g_object_class_install_property(object_class, 
> >>  PROP_CAMERA_NAME, spec);
> >>  
> >> +	GstCameraControls::installProperties(object_class, PROP_LAST);
> >>  }
> >>  
> >>  /* GstChildProxy implementation */
> >> diff --git a/src/gstreamer/meson.build 
> >> b/src/gstreamer/meson.build
> >> index c2a01e7b..6b7e53b5 100644
> >> --- a/src/gstreamer/meson.build
> >> +++ b/src/gstreamer/meson.build
> >> @@ -25,6 +25,16 @@ libcamera_gst_sources = [
> >>      'gstlibcamerasrc.cpp',
> >>  ]
> >>  
> >> +# Generate gstreamer control properties
> >> +
> >> +gen_gst_controls_template = files('gstlibcamera-controls.cpp.in')
> >> +libcamera_gst_sources += custom_target('gstlibcamera-controls.cpp',
> >> +                                       input : controls_files,
> >> +                                       output : 'gstlibcamera-controls.cpp',
> >> +                                       command : [gen_gst_controls, '-o', '@OUTPUT@',
> >> +                                                  '-t', gen_gst_controls_template, '@INPUT@'],
> >> +                                       env : py_build_env)
> >> +
> >>  libcamera_gst_cpp_args = [
> >>      '-DVERSION="@0@"'.format(libcamera_git_version),
> >>      '-DPACKAGE="@0@"'.format(meson.project_name()),
> >> diff --git a/utils/codegen/controls.py 
> >> b/utils/codegen/controls.py
> >> index 7bafee59..03c77cc6 100644
> >> --- a/utils/codegen/controls.py
> >> +++ b/utils/codegen/controls.py
> >> @@ -110,3 +110,11 @@ class Control(object):
> >>              return f"Span<const {typ}, {self.__size}>"
> >>          else:
> >>              return f"Span<const {typ}>"
> >> +
> >> +    @property
> >> +    def element_type(self):
> >> +        return self.__data.get('type')
> >
> > I wonder if we shouldn't move the existing type property to
> > extend_control() in generator scripts, and rename element_type to type.
> > This can be done on top, you don't have to address it.
> 
> I'm fine with either, although just calling it type() is a little 
> simpler for the gen-gst-controls.py script.
> 
> >> +
> >> +    @property
> >> +    def size(self):
> >> +        return self.__size
> >> diff --git a/utils/codegen/gen-gst-controls.py 
> >> b/utils/codegen/gen-gst-controls.py
> >> new file mode 100755
> >> index 00000000..5ac8981f
> >> --- /dev/null
> >> +++ b/utils/codegen/gen-gst-controls.py
> >> @@ -0,0 +1,151 @@
> >> +#!/usr/bin/env python3
> >> +# SPDX-License-Identifier: GPL-2.0-or-later
> >> +# Copyright (C) 2019, Google Inc.
> >> +# Copyright (C) 2024, Jaslo Ziska
> >> +#
> >> +# Authors:
> >> +# Laurent Pinchart <laurent.pinchart@ideasonboard.com>
> >> +# Jaslo Ziska <jaslo@ziska.de>
> >> +#
> >> +# Generate gstreamer control properties from YAML
> >> +
> >> +import argparse
> >> +import jinja2
> >> +import re
> >> +import sys
> >> +import yaml
> >> +
> >> +from controls import Control
> >> +
> >> +
> >> +def find_common_prefix(strings):
> >> +    prefix = strings[0]
> >> +
> >> +    for string in strings[1:]:
> >> +        while string[:len(prefix)] != prefix and prefix:
> >> +            prefix = prefix[:len(prefix) - 1]
> >> +        if not prefix:
> >> +            break
> >> +
> >> +    return prefix
> >> +
> >> +
> >> +def format_description(description):
> >> +    # Substitute doxygen keywords \sa (see also) and \todo
> >> +    description = re.sub(r'\\sa((?: \w+)+)',
> >> +                         lambda match: 'See also: ' + ', '.join(
> >> +                             map(kebab_case, match.group(1).strip().split(' '))
> >> +                         ) + '.', description)
> >> +    description = re.sub(r'\\todo', 'Todo:', description)
> >> +
> >> +    description = description.strip().split('\n')
> >> +    return '\n'.join([
> >> +        '"' + line.replace('\\', r'\\').replace('"', r'\"') + ' "' for line in description if line
> >> +    ]).rstrip()
> >> +
> >> +
> >> +def snake_case(s):
> >> +    return ''.join([
> >> +        c.isupper() and ('_' + c.lower()) or c for c in s
> >> +    ]).strip('_')
> >> +
> >> +
> >> +def kebab_case(s):
> >> +    return snake_case(s).replace('_', '-')
> >> +
> >> +
> >> +def extend_control(ctrl):
> >> +    if ctrl.vendor != 'libcamera':
> >> +        ctrl.namespace = f'{ctrl.vendor}::'
> >> +        ctrl.vendor_prefix = f'{ctrl.vendor}-'
> >> +    else:
> >> +        ctrl.namespace = ''
> >> +        ctrl.vendor_prefix = ''
> >> +
> >> +    ctrl.is_array = ctrl.size is not None
> >> +
> >> +    if ctrl.is_enum:
> >> +        # remove common prefix from enum variant names
> >
> > s/# remove/# Remove/
> >
> >> +        prefix = find_common_prefix([enum.name for enum in ctrl.enum_values])
> >> +        for enum in ctrl.enum_values:
> >> +            enum.gst_name = kebab_case(enum.name.removeprefix(prefix))
> >> +
> >> +        ctrl.gtype = 'enum'
> >> +        ctrl.default = '0'
> >> +    elif ctrl.element_type == 'bool':
> >> +        ctrl.gtype = 'boolean'
> >> +        ctrl.default = 'false'
> >> +    elif ctrl.element_type == 'float':
> >> +        ctrl.gtype = 'float'
> >> +        ctrl.default = '0'
> >> +        ctrl.min = '-G_MAXFLOAT'
> >> +        ctrl.max = 'G_MAXFLOAT'
> >> +    elif ctrl.element_type == 'int32_t':
> >> +        ctrl.gtype = 'int'
> >> +        ctrl.default = '0'
> >> +        ctrl.min = 'G_MININT'
> >> +        ctrl.max = 'G_MAXINT'
> >> +    elif ctrl.element_type == 'int64_t':
> >> +        ctrl.gtype = 'int64'
> >> +        ctrl.default = '0'
> >> +        ctrl.min = 'G_MININT64'
> >> +        ctrl.max = 'G_MAXINT64'
> >> +    elif ctrl.element_type == 'uint8_t':
> >> +        ctrl.gtype = 'uchar'
> >> +        ctrl.default = '0'
> >> +        ctrl.min = '0'
> >> +        ctrl.max = 'G_MAXUINT8'
> >> +    elif ctrl.element_type == 'Rectangle':
> >> +        ctrl.is_rectangle = True
> >> +        ctrl.default = '0'
> >> +        ctrl.min = '0'
> >> +        ctrl.max = 'G_MAXINT'
> >> +    else:
> >> +        raise RuntimeError(f'The type `{ctrl.element_type}` is unknown')
> >> +
> >> +    return ctrl
> >> +
> >> +
> >> +def main(argv):
> >> +    # Parse command line arguments
> >> +    parser = argparse.ArgumentParser()
> >> +    parser.add_argument('--output', '-o', metavar='file', type=str,
> >> +                        help='Output file name. Defaults to standard output if not specified.')
> >> +    parser.add_argument('--template', '-t', dest='template', type=str, required=True,
> >> +                        help='Template file name.')
> >> +    parser.add_argument('input', type=str, nargs='+',
> >> +                        help='Input file name.')
> >> +
> >> +    args = parser.parse_args(argv[1:])
> >> +
> >> +    controls = {}
> >> +    for input in args.input:
> >> +        data = yaml.safe_load(open(input, 'rb').read())
> >> +
> >> +        vendor = data['vendor']
> >> +        ctrls = controls.setdefault(vendor, [])
> >> +
> >> +        for ctrl in data['controls']:
> >> +            ctrl = Control(*ctrl.popitem(), vendor)
> >> +            ctrls.append(extend_control(ctrl))
> >> +
> >> +    data = {'controls': list(controls.items())}
> >> +
> >> +    env = jinja2.Environment()
> >> +    env.filters['format_description'] = format_description
> >> +    env.filters['snake_case'] = snake_case
> >> +    env.filters['kebab_case'] = kebab_case
> >> +    template = env.from_string(open(args.template, 'r', encoding='utf-8').read())
> >> +    string = template.render(data)
> >> +
> >> +    if args.output:
> >> +        with open(args.output, 'w', encoding='utf-8') as output:
> >> +            output.write(string)
> >> +    else:
> >> +        sys.stdout.write(string)
> >> +
> >> +    return 0
> >> +
> >> +
> >> +if __name__ == '__main__':
> >> +    sys.exit(main(sys.argv))
> >> diff --git a/utils/codegen/meson.build 
> >> b/utils/codegen/meson.build
> >> index adf33bba..904dd66d 100644
> >> --- a/utils/codegen/meson.build
> >> +++ b/utils/codegen/meson.build
> >> @@ -11,6 +11,7 @@ py_modules += ['jinja2', 'yaml']
> >>  
> >>  gen_controls = files('gen-controls.py')
> >>  gen_formats = files('gen-formats.py')
> >> +gen_gst_controls = files('gen-gst-controls.py')
> >>  gen_header = files('gen-header.sh')
> >>  gen_ipa_pub_key = files('gen-ipa-pub-key.py')
> >>  gen_tracepoints = files('gen-tp-header.py')