[v2.1,4/7] Documentation: Breakout docs.rst

20943 diff mbox series

In preparation for including more of the Documentation for libcamera
on the website, break out the Camera Stack and Feature Requirements
sections of docs.rst file into separate files for each section. Add
all of the new files to documentation-contents.rst so they're
included on the website too.

Signed-off-by: Daniel Scally <dan.scally@ideasonboard.com>
---
Changes since v2:

	- Fixed the docs_sources array

Changes since v1:

	- Included the new files in meson's docs_sources array

 Documentation/camera_stack.rst           |  78 ++++++++
 Documentation/docs.rst                   | 219 -----------------------
 Documentation/documentation-contents.rst |   2 +
 Documentation/feature_requirements.rst   | 145 +++++++++++++++
 Documentation/index.rst                  |   2 +
 Documentation/meson.build                |   2 +
 6 files changed, 229 insertions(+), 219 deletions(-)
 create mode 100644 Documentation/camera_stack.rst
 create mode 100644 Documentation/feature_requirements.rst

Hi Dan,

Thank you for the patch.

On Thu, Aug 15, 2024 at 10:59:31AM +0100, Daniel Scally wrote:
> In preparation for including more of the Documentation for libcamera
> on the website, break out the Camera Stack and Feature Requirements
> sections of docs.rst file into separate files for each section. Add
> all of the new files to documentation-contents.rst so they're
> included on the website too.
> 
> Signed-off-by: Daniel Scally <dan.scally@ideasonboard.com>
> ---
> Changes since v2:
> 
> 	- Fixed the docs_sources array
> 
> Changes since v1:
> 
> 	- Included the new files in meson's docs_sources array
> 
>  Documentation/camera_stack.rst           |  78 ++++++++
>  Documentation/docs.rst                   | 219 -----------------------
>  Documentation/documentation-contents.rst |   2 +
>  Documentation/feature_requirements.rst   | 145 +++++++++++++++
>  Documentation/index.rst                  |   2 +
>  Documentation/meson.build                |   2 +
>  6 files changed, 229 insertions(+), 219 deletions(-)
>  create mode 100644 Documentation/camera_stack.rst
>  create mode 100644 Documentation/feature_requirements.rst
> 
> diff --git a/Documentation/camera_stack.rst b/Documentation/camera_stack.rst
> new file mode 100644
> index 00000000..381385cb
> --- /dev/null
> +++ b/Documentation/camera_stack.rst
> @@ -0,0 +1,78 @@
> +.. SPDX-License-Identifier: CC-BY-SA-4.0
> +
> +.. include:: documentation-contents.rst
> +
> +Camera Stack
> +============
> +
> +::
> +
> +    a c /    +-------------+  +-------------+  +-------------+  +-------------+
> +    p a |    |   Native    |  |  Framework  |  |   Native    |  |   Android   |
> +    p t |    |    V4L2     |  | Application |  |  libcamera  |  |   Camera    |
> +    l i |    | Application |  | (gstreamer) |  | Application |  |  Framework  |
> +    i o \    +-------------+  +-------------+  +-------------+  +-------------+
> +      n             ^                ^                ^                ^
> +                    |                |                |                |
> +    l a             |                |                |                |
> +    i d             v                v                |                v
> +    b a /    +-------------+  +-------------+         |         +-------------+
> +    c p |    |    V4L2     |  |   Camera    |         |         |   Android   |
> +    a t |    |   Compat.   |  |  Framework  |         |         |   Camera    |
> +    m a |    |             |  | (gstreamer) |         |         |     HAL     |
> +    e t \    +-------------+  +-------------+         |         +-------------+
> +    r i             ^                ^                |                ^
> +    a o             |                |                |                |
> +      n             |                |                |                |
> +        /           |         ,................................................
> +        |           |         !      :            Language             :      !
> +    l f |           |         !      :            Bindings             :      !
> +    i r |           |         !      :           (optional)            :      !
> +    b a |           |         \...............................................'
> +    c m |           |                |                |                |
> +    a e |           |                |                |                |
> +    m w |           v                v                v                v
> +    e o |    +----------------------------------------------------------------+
> +    r r |    |                                                                |
> +    a k |    |                           libcamera                            |
> +        |    |                                                                |
> +        \    +----------------------------------------------------------------+
> +                            ^                  ^                  ^
> +    Userspace               |                  |                  |
> +   ------------------------ | ---------------- | ---------------- | ---------------
> +    Kernel                  |                  |                  |
> +                            v                  v                  v
> +                      +-----------+      +-----------+      +-----------+
> +                      |   Media   | <--> |   Video   | <--> |   V4L2    |
> +                      |  Device   |      |  Device   |      |  Subdev   |
> +                      +-----------+      +-----------+      +-----------+
> +
> +The camera stack comprises four software layers. From bottom to top:
> +
> +* The kernel drivers control the camera hardware and expose a
> +  low-level interface to userspace through the Linux kernel V4L2
> +  family of APIs (Media Controller API, V4L2 Video Device API and
> +  V4L2 Subdev API).
> +
> +* The libcamera framework is the core part of the stack. It
> +  handles all control of the camera devices in its core component,
> +  libcamera, and exposes a native C++ API to upper layers. Optional
> +  language bindings allow interfacing to libcamera from other
> +  programming languages.
> +
> +  Those components live in the same source code repository and
> +  all together constitute the libcamera framework.
> +
> +* The libcamera adaptation is an umbrella term designating the
> +  components that interface to libcamera in other frameworks.
> +  Notable examples are a V4L2 compatibility layer, a gstreamer
> +  libcamera element, and an Android camera HAL implementation based
> +  on libcamera.
> +
> +  Those components can live in the libcamera project source code
> +  in separate repositories, or move to their respective project's
> +  repository (for instance the gstreamer libcamera element).
> +
> +* The applications and upper level frameworks are based on the
> +  libcamera framework or libcamera adaptation, and are outside of
> +  the scope of the libcamera project.
> diff --git a/Documentation/docs.rst b/Documentation/docs.rst
> index 10f07a9e..d65b2b4f 100644
> --- a/Documentation/docs.rst
> +++ b/Documentation/docs.rst
> @@ -21,225 +21,6 @@ The libcamera API is extensively documented using Doxygen. The :ref:`API
>  nightly build <api>` contains the most up-to-date API documentation, built from
>  the latest master branch.
>  
> -Feature Requirements
> -====================
> -
> -Device enumeration
> -------------------
> -
> -The library shall support enumerating all camera devices available in the
> -system, including both fixed cameras and hotpluggable cameras. It shall
> -support cameras plugged and unplugged after the initialization of the
> -library, and shall offer a mechanism to notify applications of camera plug
> -and unplug.
> -
> -The following types of cameras shall be supported:
> -
> -* Internal cameras designed for point-and-shoot still image and video
> -  capture usage, either controlled directly by the CPU, or exposed through
> -  an internal USB bus as a UVC device.
> -
> -* External UVC cameras designed for video conferencing usage.
> -
> -Other types of camera, including analog cameras, depth cameras, thermal
> -cameras, external digital picture or movie cameras, are out of scope for
> -this project.
> -
> -A hardware device that includes independent camera sensors, such as front
> -and back sensors in a phone, shall be considered as multiple camera devices
> -for the purpose of this library.
> -
> -Independent Camera Devices
> ---------------------------
> -
> -When multiple cameras are present in the system and are able to operate
> -independently from each other, the library shall expose them as multiple
> -camera devices and support parallel operation without any additional usage
> -restriction apart from the limitations inherent to the hardware (such as
> -memory bandwidth, CPU usage or number of CSI-2 receivers for instance).
> -
> -Independent processes shall be able to use independent cameras devices
> -without interfering with each other. A single camera device shall be
> -usable by a single process at a time.
> -
> -Multiple streams support
> -------------------------
> -
> -The library shall support multiple video streams running in parallel
> -for each camera device, within the limits imposed by the system.
> -
> -Per frame controls
> -------------------
> -
> -The library shall support controlling capture parameters for each stream
> -on a per-frame basis, on a best effort basis based on the capabilities of the
> -hardware and underlying software stack (including kernel drivers and
> -firmware). It shall apply capture parameters to the frame they target, and
> -report the value of the parameters that have effectively been used for each
> -captured frame.
> -
> -When a camera device supports multiple streams, the library shall allow both
> -control of each stream independently, and control of multiple streams
> -together. Streams that are controlled together shall be synchronized. No
> -synchronization is required for streams controlled independently.
> -
> -Capability Enumeration
> -----------------------
> -
> -The library shall expose capabilities of each camera device in a way that
> -allows applications to discover those capabilities dynamically. Applications
> -shall be allowed to cache capabilities for as long as they are using the
> -library. If capabilities can change at runtime, the library shall offer a
> -mechanism to notify applications of such changes. Applications shall not
> -cache capabilities in long term storage between runs.
> -
> -Capabilities shall be discovered dynamically at runtime from the device when
> -possible, and may come, in part or in full, from platform configuration
> -data.
> -
> -Device Profiles
> ----------------
> -
> -The library may define different camera device profiles, each with a minimum
> -set of required capabilities. Applications may use those profiles to quickly
> -determine the level of features exposed by a device without parsing the full
> -list of capabilities. Camera devices may implement additional capabilities
> -on top of the minimum required set for the profile they expose.
> -
> -3A and Image Enhancement Algorithms
> ------------------------------------
> -
> -The camera devices shall implement auto exposure, auto gain and auto white
> -balance. Camera devices that include a focus lens shall implement auto
> -focus. Additional image enhancement algorithms, such as noise reduction or
> -video stabilization, may be implemented.
> -
> -All algorithms may be implemented in hardware or firmware outside of the
> -library, or in software in the library. They shall all be controllable by
> -applications.
> -
> -The library shall be architectured to isolate the 3A and image enhancement
> -algorithms in a component with a documented API, respectively called the 3A
> -component and the 3A API. The 3A API shall be stable, and shall allow both
> -open-source and closed-source implementations of the 3A component.
> -
> -The library may include statically-linked open-source 3A components, and
> -shall support dynamically-linked open-source and closed-source 3A
> -components.
> -
> -Closed-source 3A Component Sandboxing
> --------------------------------------
> -
> -For security purposes, it may be desired to run closed-source 3A components
> -in a separate process. The 3A API would in such a case be transported over
> -IPC. The 3A API shall make it possible to use any IPC mechanism that
> -supports passing file descriptors.
> -
> -The library may implement an IPC mechanism, and shall support third-party
> -platform-specific IPC mechanisms through the implementation of a
> -platform-specific 3A API wrapper. No modification to the library shall be
> -needed to use such third-party IPC mechanisms.
> -
> -The 3A component shall not directly access any device node on the system.
> -Such accesses shall instead be performed through the 3A API. The library
> -shall validate all accesses and restrict them to what is absolutely required
> -by 3A components.
> -
> -V4L2 Compatibility Layer
> -------------------------
> -
> -The project shall support traditional V4L2 application through an additional
> -libcamera wrapper library. The wrapper library shall trap all accesses to
> -camera devices through `LD_PRELOAD`, and route them through libcamera to
> -emulate a high-level V4L2 camera device. It shall expose camera device
> -features on a best-effort basis, and aim for the level of features
> -traditionally available from a UVC camera designed for video conferencing.
> -
> -Android Camera HAL v3 Compatibility
> ------------------------------------
> -
> -The library API shall expose all the features required to implement an
> -Android Camera HAL v3 on top of libcamera. Some features of the HAL may be
> -omitted as long as they can be implemented separately in the HAL, such as
> -JPEG encoding, or YUV reprocessing.
> -
> -
> -Camera Stack
> -============
> -
> -::
> -
> -    a c /    +-------------+  +-------------+  +-------------+  +-------------+
> -    p a |    |   Native    |  |  Framework  |  |   Native    |  |   Android   |
> -    p t |    |    V4L2     |  | Application |  |  libcamera  |  |   Camera    |
> -    l i |    | Application |  | (gstreamer) |  | Application |  |  Framework  |
> -    i o \    +-------------+  +-------------+  +-------------+  +-------------+
> -      n             ^                ^                ^                ^
> -                    |                |                |                |
> -    l a             |                |                |                |
> -    i d             v                v                |                v
> -    b a /    +-------------+  +-------------+         |         +-------------+
> -    c p |    |    V4L2     |  |   Camera    |         |         |   Android   |
> -    a t |    |   Compat.   |  |  Framework  |         |         |   Camera    |
> -    m a |    |             |  | (gstreamer) |         |         |     HAL     |
> -    e t \    +-------------+  +-------------+         |         +-------------+
> -    r i             ^                ^                |                ^
> -    a o             |                |                |                |
> -      n             |                |                |                |
> -        /           |         ,................................................
> -        |           |         !      :            Language             :      !
> -    l f |           |         !      :            Bindings             :      !
> -    i r |           |         !      :           (optional)            :      !
> -    b a |           |         \...............................................'
> -    c m |           |                |                |                |
> -    a e |           |                |                |                |
> -    m w |           v                v                v                v
> -    e o |    +----------------------------------------------------------------+
> -    r r |    |                                                                |
> -    a k |    |                           libcamera                            |
> -        |    |                                                                |
> -        \    +----------------------------------------------------------------+
> -                            ^                  ^                  ^
> -    Userspace               |                  |                  |
> -   ------------------------ | ---------------- | ---------------- | ---------------
> -    Kernel                  |                  |                  |
> -                            v                  v                  v
> -                      +-----------+      +-----------+      +-----------+
> -                      |   Media   | <--> |   Video   | <--> |   V4L2    |
> -                      |  Device   |      |  Device   |      |  Subdev   |
> -                      +-----------+      +-----------+      +-----------+
> -
> -The camera stack comprises four software layers. From bottom to top:
> -
> -* The kernel drivers control the camera hardware and expose a
> -  low-level interface to userspace through the Linux kernel V4L2
> -  family of APIs (Media Controller API, V4L2 Video Device API and
> -  V4L2 Subdev API).
> -
> -* The libcamera framework is the core part of the stack. It
> -  handles all control of the camera devices in its core component,
> -  libcamera, and exposes a native C++ API to upper layers. Optional
> -  language bindings allow interfacing to libcamera from other
> -  programming languages.
> -
> -  Those components live in the same source code repository and
> -  all together constitute the libcamera framework.
> -
> -* The libcamera adaptation is an umbrella term designating the
> -  components that interface to libcamera in other frameworks.
> -  Notable examples are a V4L2 compatibility layer, a gstreamer
> -  libcamera element, and an Android camera HAL implementation based
> -  on libcamera.
> -
> -  Those components can live in the libcamera project source code
> -  in separate repositories, or move to their respective project's
> -  repository (for instance the gstreamer libcamera element).
> -
> -* The applications and upper level frameworks are based on the
> -  libcamera framework or libcamera adaptation, and are outside of
> -  the scope of the libcamera project.
> -
> -
>  libcamera Architecture
>  ======================
>  
> diff --git a/Documentation/documentation-contents.rst b/Documentation/documentation-contents.rst
> index a6915e05..613366d1 100644
> --- a/Documentation/documentation-contents.rst
> +++ b/Documentation/documentation-contents.rst
> @@ -4,9 +4,11 @@
>  
>     * :doc:`/api-html/index`
>     * :doc:`/camera-sensor-model`
> +   * :doc:`/camera_stack`
>     * :doc:`/code-of-conduct`
>     * :doc:`/coding-style`
>     * :doc:`/environment_variables`
> +   * :doc:`/feature_requirements`
>     * :doc:`/guides/application-developer`
>     * :doc:`/guides/introduction`
>     * :doc:`/guides/ipa`
> diff --git a/Documentation/feature_requirements.rst b/Documentation/feature_requirements.rst
> new file mode 100644
> index 00000000..cae7e9ab
> --- /dev/null
> +++ b/Documentation/feature_requirements.rst
> @@ -0,0 +1,145 @@
> +.. SPDX-License-Identifier: CC-BY-SA-4.0
> +
> +.. include:: documentation-contents.rst
> +
> +Feature Requirements
> +====================

We should revisit all this at some point, but that's out of scope for
this series.

> +
> +Device enumeration
> +------------------
> +
> +The library shall support enumerating all camera devices available in the
> +system, including both fixed cameras and hotpluggable cameras. It shall
> +support cameras plugged and unplugged after the initialization of the
> +library, and shall offer a mechanism to notify applications of camera plug
> +and unplug.
> +
> +The following types of cameras shall be supported:
> +
> +* Internal cameras designed for point-and-shoot still image and video
> +  capture usage, either controlled directly by the CPU, or exposed through
> +  an internal USB bus as a UVC device.
> +
> +* External UVC cameras designed for video conferencing usage.
> +
> +Other types of camera, including analog cameras, depth cameras, thermal
> +cameras, external digital picture or movie cameras, are out of scope for
> +this project.
> +
> +A hardware device that includes independent camera sensors, such as front
> +and back sensors in a phone, shall be considered as multiple camera devices
> +for the purpose of this library.
> +
> +Independent Camera Devices
> +--------------------------
> +
> +When multiple cameras are present in the system and are able to operate
> +independently from each other, the library shall expose them as multiple
> +camera devices and support parallel operation without any additional usage
> +restriction apart from the limitations inherent to the hardware (such as
> +memory bandwidth, CPU usage or number of CSI-2 receivers for instance).
> +
> +Independent processes shall be able to use independent cameras devices
> +without interfering with each other. A single camera device shall be
> +usable by a single process at a time.
> +
> +Multiple streams support
> +------------------------
> +
> +The library shall support multiple video streams running in parallel
> +for each camera device, within the limits imposed by the system.
> +
> +Per frame controls
> +------------------
> +
> +The library shall support controlling capture parameters for each stream
> +on a per-frame basis, on a best effort basis based on the capabilities of the
> +hardware and underlying software stack (including kernel drivers and
> +firmware). It shall apply capture parameters to the frame they target, and
> +report the value of the parameters that have effectively been used for each
> +captured frame.
> +
> +When a camera device supports multiple streams, the library shall allow both
> +control of each stream independently, and control of multiple streams
> +together. Streams that are controlled together shall be synchronized. No
> +synchronization is required for streams controlled independently.
> +
> +Capability Enumeration
> +----------------------
> +
> +The library shall expose capabilities of each camera device in a way that
> +allows applications to discover those capabilities dynamically. Applications
> +shall be allowed to cache capabilities for as long as they are using the
> +library. If capabilities can change at runtime, the library shall offer a
> +mechanism to notify applications of such changes. Applications shall not
> +cache capabilities in long term storage between runs.
> +
> +Capabilities shall be discovered dynamically at runtime from the device when
> +possible, and may come, in part or in full, from platform configuration
> +data.
> +
> +Device Profiles
> +---------------
> +
> +The library may define different camera device profiles, each with a minimum
> +set of required capabilities. Applications may use those profiles to quickly
> +determine the level of features exposed by a device without parsing the full
> +list of capabilities. Camera devices may implement additional capabilities
> +on top of the minimum required set for the profile they expose.
> +
> +3A and Image Enhancement Algorithms
> +-----------------------------------
> +
> +The camera devices shall implement auto exposure, auto gain and auto white
> +balance. Camera devices that include a focus lens shall implement auto
> +focus. Additional image enhancement algorithms, such as noise reduction or
> +video stabilization, may be implemented.
> +
> +All algorithms may be implemented in hardware or firmware outside of the
> +library, or in software in the library. They shall all be controllable by
> +applications.
> +
> +The library shall be architectured to isolate the 3A and image enhancement
> +algorithms in a component with a documented API, respectively called the 3A
> +component and the 3A API. The 3A API shall be stable, and shall allow both
> +open-source and closed-source implementations of the 3A component.
> +
> +The library may include statically-linked open-source 3A components, and
> +shall support dynamically-linked open-source and closed-source 3A
> +components.
> +
> +Closed-source 3A Component Sandboxing
> +-------------------------------------
> +
> +For security purposes, it may be desired to run closed-source 3A components
> +in a separate process. The 3A API would in such a case be transported over
> +IPC. The 3A API shall make it possible to use any IPC mechanism that
> +supports passing file descriptors.
> +
> +The library may implement an IPC mechanism, and shall support third-party
> +platform-specific IPC mechanisms through the implementation of a
> +platform-specific 3A API wrapper. No modification to the library shall be
> +needed to use such third-party IPC mechanisms.
> +
> +The 3A component shall not directly access any device node on the system.
> +Such accesses shall instead be performed through the 3A API. The library
> +shall validate all accesses and restrict them to what is absolutely required
> +by 3A components.
> +
> +V4L2 Compatibility Layer
> +------------------------
> +
> +The project shall support traditional V4L2 application through an additional
> +libcamera wrapper library. The wrapper library shall trap all accesses to
> +camera devices through `LD_PRELOAD`, and route them through libcamera to
> +emulate a high-level V4L2 camera device. It shall expose camera device
> +features on a best-effort basis, and aim for the level of features
> +traditionally available from a UVC camera designed for video conferencing.
> +
> +Android Camera HAL v3 Compatibility
> +-----------------------------------
> +
> +The library API shall expose all the features required to implement an
> +Android Camera HAL v3 on top of libcamera. Some features of the HAL may be
> +omitted as long as they can be implemented separately in the HAL, such as
> +JPEG encoding, or YUV reprocessing.
> diff --git a/Documentation/index.rst b/Documentation/index.rst
> index 52ddc494..59416906 100644
> --- a/Documentation/index.rst
> +++ b/Documentation/index.rst
> @@ -16,8 +16,10 @@
>  
>     Application Writer's Guide <guides/application-developer>
>     Camera Sensor Model <camera-sensor-model>
> +   Camera Stack <camera_stack>
>     Developer Guide <guides/introduction>
>     Environment variables <environment_variables>
> +   Feature Requirements <feature_requirements>
>     IPA Writer's guide <guides/ipa>
>     Lens driver requirements <lens_driver_requirements>
>     Pipeline Handler Writer's Guide <guides/pipeline-handler>
> diff --git a/Documentation/meson.build b/Documentation/meson.build
> index c5736991..bf5a80bd 100644
> --- a/Documentation/meson.build
> +++ b/Documentation/meson.build
> @@ -124,6 +124,7 @@ endif
>  if sphinx.found()
>      docs_sources = [
>          'camera-sensor-model.rst',
> +	'camera_stack.rst',

checkstyle.py should have warned you. Same below. Apart from that,

Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>

>          'code-of-conduct.rst',
>          'coding-style.rst',
>          'conf.py',
> @@ -131,6 +132,7 @@ if sphinx.found()
>          'docs.rst',
>  	'documentation-contents.rst',
>          'environment_variables.rst',
> +	'feature_requirements.rst',
>          'guides/application-developer.rst',
>          'guides/introduction.rst',
>          'guides/ipa.rst',