[libcamera-devel,v3,05/16] libcamera: formats: Add ImageFormats

1436 diff mbox series

Add a new class to hold format information for v4l2 devices and
subdevices. The object describes the relationship between either pixel
formats (v4l2 devices) or media bus codes (v4l2 subdevice) and a list of
image sizes which can be produced with that format.

Signed-off-by: Niklas Söderlund <niklas.soderlund@ragnatech.se>
---
 src/libcamera/formats.cpp       | 80 +++++++++++++++++++++++++++++++++
 src/libcamera/include/formats.h | 14 ++++++
 2 files changed, 94 insertions(+)

Hi Niklas,

Thank you for the patch.

On Sun, Jun 16, 2019 at 03:33:51PM +0200, Niklas Söderlund wrote:
> Add a new class to hold format information for v4l2 devices and

s/v4l2/V4L2/ (and possibly "V4L2 video devices and subdevices" depending
on which series gets merged first)

> subdevices. The object describes the relationship between either pixel
> formats (v4l2 devices) or media bus codes (v4l2 subdevice) and a list of

V4L2 there too.

> image sizes which can be produced with that format.
> 
> Signed-off-by: Niklas Söderlund <niklas.soderlund@ragnatech.se>
> ---
>  src/libcamera/formats.cpp       | 80 +++++++++++++++++++++++++++++++++
>  src/libcamera/include/formats.h | 14 ++++++
>  2 files changed, 94 insertions(+)
> 
> diff --git a/src/libcamera/formats.cpp b/src/libcamera/formats.cpp
> index 56f4ddb51ffad4d3..2fd0c5480324ce33 100644
> --- a/src/libcamera/formats.cpp
> +++ b/src/libcamera/formats.cpp
> @@ -24,4 +24,84 @@ namespace libcamera {
>   * resolutions represented by SizeRange items.
>   */
>  
> +/**
> + * \class ImageFormats
> + * \brief Describe V4L2Device and V4L2SubDevice image formats
> + *
> + * The class describes information about image formats and supported sizes. If
> + * the ImageFormat describe a V4L2Device the image formats are described with a
> + * fourcc pixel format code, while if it describes a V4L2SubDevice the formats
> + * are described with media bus codes, both defined by the V4L2 specification.

I would propose

"This class stores a list of image formats, each associated with a
corresponding set of image sizes. It is used to describe the formats and
sizes supported by a V4L2Device or V4L2Subdevice.

Formats are stored as an integer. When used for a V4L2Device, the image
formats are fourcc pixel formats. When used for a V4L2Subdevice they are
media bus codes. Both are defined by the V4L2 specification.

Sizes are stored as a list of SizeRange."

> + */
> +
> +/**
> + * \brief Add a format and sizes to the description

s/and sizes/and corresponding sizes/

> + * \param[in] format Pixel format or media bus code to describe
> + * \param[in] sizes List of supported sizes for the format

s/sizes/size ranges/ ?

> + *
> + * \return 0 on success or a negative error code otherwise
> + * \retval -EBUSY The format is already described

I wonder if we really need this, or if we should ignore the error
silently. If you think it should be kept, I would use -EEXIST.

> + */
> +int ImageFormats::addFormat(unsigned int format, const std::vector<SizeRange> &sizes)
> +{
> +	if (data_.find(format) != data_.end())
> +		return -EBUSY;
> +
> +	data_[format] = sizes;
> +
> +	return 0;
> +}
> +
> +/**
> + * \brief Check if the list of devices supported formats is empty
> + * \return True if the list of supported formats is empty
> + */
> +bool ImageFormats::isEmpty() const
> +{
> +	return data_.empty();
> +}
> +
> +/**
> + * \brief Retrieve a list of all supported image formats
> + * \return List of pixel formats or media bus codes
> + */
> +std::vector<unsigned int> ImageFormats::formats() const
> +{
> +	std::vector<unsigned int> formats;
> +	formats.reserve(data_.size());
> +
> +	for (auto const &it : data_)
> +		formats.push_back(it.first);
> +
> +	return formats;

Do you think it would make sense to cache it internally and return a
const reference, or is it not worth it given the existing and foreseen
use cases ? If you think it could be useful you don't have to fix it
now, but a \todo would be useful.

> +}
> +
> +/**
> + * \brief Retrieve all sizes for a specific format
> + * \param[in] format A pixelformat or mbus code

s/A/The/

> + *
> + * Retrieve all SizeRanges for a specific format. For V4L2Device \a format is a

s/SizeRanges/size ranges/ or SizeRange instances (I would go for the
format). The return value type in doxygen will offer a clickable link to
SizeRange, so there's no strict need to mention SizeRange in the text
here.

> + * pixel format while for a V4L2Subdevice \a format is a media bus code.
> + *
> + * \return he list of image sizes produced using \a format, or an empty list if

s/he/The/
s/produced using/supported for/ ?

> + * format is not supported

s/format/the format/

> + */
> +std::vector<SizeRange> ImageFormats::sizes(unsigned int format) const
> +{
> +	auto const &it = data_.find(format);
> +	if (it == data_.end())
> +		return {};
> +
> +	return it->second;

In this case I think a copy is quite overkill. You could declare

	static std::vector<SizeRange> empty;

replace return {} with return empty, and change the function type to
return a const reference.

> +}
> +
> +/**
> + * \brief Retrieve the map that associates formats to image sizes
> + * \return Map that associates formats to image sizes

s/Map/The map/

With these small issues addressed,

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

> + */
> +const std::map<unsigned int, std::vector<SizeRange>> &ImageFormats::data() const
> +{
> +	return data_;
> +}
> +
>  } /* namespace libcamera */
> diff --git a/src/libcamera/include/formats.h b/src/libcamera/include/formats.h
> index a73772b1eda068b4..a49f83f3d8d60621 100644
> --- a/src/libcamera/include/formats.h
> +++ b/src/libcamera/include/formats.h
> @@ -17,6 +17,20 @@ namespace libcamera {
>  
>  typedef std::map<unsigned int, std::vector<SizeRange>> FormatEnum;
>  
> +class ImageFormats
> +{
> +public:
> +	int addFormat(unsigned int format, const std::vector<SizeRange> &sizes);
> +
> +	bool isEmpty() const;
> +	std::vector<unsigned int> formats() const;
> +	std::vector<SizeRange> sizes(unsigned int format) const;
> +	const std::map<unsigned int, std::vector<SizeRange>> &data() const;
> +
> +private:
> +	std::map<unsigned int, std::vector<SizeRange>> data_;
> +};
> +
>  } /* namespace libcamera */
>  
>  #endif /* __LIBCAMERA_FORMATS_H__ */