[libcamera-devel] [PATCH v3 08/13] libcamera: v4l2_subdevice: Add format information

Sat Apr 25 22:29:03 CEST 2020

Hi Jacopo,

Thank you for the patch.

On Fri, Apr 24, 2020 at 11:52:59PM +0200, Jacopo Mondi wrote:
> Define a map of static information associated with a media bus code.
> Start by reporting the bits-per-pixel for each media bus code defined by
> the V4L2 kernel API, to later expand it when necessary.
> 
> Add to the V4L2SubdeviceFormat class a method to return the bits per
> pixel, retrieved by inspecting the static map of format information.
> 
> Signed-off-by: Jacopo Mondi <jacopo at jmondi.org>
> ---
>  src/libcamera/include/v4l2_subdevice.h |   3 +
>  src/libcamera/v4l2_subdevice.cpp       | 113 +++++++++++++++++++++++++
>  2 files changed, 116 insertions(+)
> 
> diff --git a/src/libcamera/include/v4l2_subdevice.h b/src/libcamera/include/v4l2_subdevice.h
> index 763ffadb61fb..43953a0a5a6c 100644
> --- a/src/libcamera/include/v4l2_subdevice.h
> +++ b/src/libcamera/include/v4l2_subdevice.h
> @@ -23,10 +23,13 @@ namespace libcamera {
>  class MediaDevice;
>  
>  struct V4L2SubdeviceFormat {
> +	using infoMap = std::map<uint32_t, uint8_t>;

There's no need to define a type here as it's not used in the API, you
can use it directly below.

> +
>  	uint32_t mbus_code;
>  	Size size;
>  
>  	const std::string toString() const;
> +	uint8_t bitsPerPixel() const;
>  };
>  
>  class V4L2Subdevice : public V4L2Device
> diff --git a/src/libcamera/v4l2_subdevice.cpp b/src/libcamera/v4l2_subdevice.cpp
> index 4dcf8ce48754..6f72c363fc7f 100644
> --- a/src/libcamera/v4l2_subdevice.cpp
> +++ b/src/libcamera/v4l2_subdevice.cpp
> @@ -14,6 +14,7 @@
>  #include <sys/ioctl.h>
>  #include <unistd.h>
>  
> +#include <linux/media-bus-format.h>
>  #include <linux/v4l2-subdev.h>
>  
>  #include <libcamera/geometry.h>
> @@ -32,6 +33,92 @@ namespace libcamera {
>  
>  LOG_DECLARE_CATEGORY(V4L2)
>  
> +namespace {
> +
> +/*
> + * \var formatInfoMap
> + * \brief A map that associates information to V4L2 media bus codes
> + */

No need for doxygen doc (that would require /** instead of /*) as it's
purely internal.

> +const V4L2SubdeviceFormat::infoMap formatInfoMap = {

So here we would have

const std::map<uint32_t, uint8_t> formatInfoMap = {

> +	{ V4L2_MBUS_FMT_RGB444_2X8_PADHI_BE, 16 },
> +	{ V4L2_MBUS_FMT_RGB444_2X8_PADHI_LE, 16 },
> +	{ V4L2_MBUS_FMT_RGB555_2X8_PADHI_BE, 16 },
> +	{ V4L2_MBUS_FMT_RGB555_2X8_PADHI_LE, 16 },
> +	{ V4L2_MBUS_FMT_BGR565_2X8_BE, 16 },
> +	{ V4L2_MBUS_FMT_BGR565_2X8_LE, 16 },
> +	{ V4L2_MBUS_FMT_RGB565_2X8_BE, 16 },
> +	{ V4L2_MBUS_FMT_RGB565_2X8_LE, 16 },
> +	{ V4L2_MBUS_FMT_RGB666_1X18, 18 },
> +	{ V4L2_MBUS_FMT_RGB888_1X24, 24 },
> +	{ V4L2_MBUS_FMT_RGB888_2X12_BE, 24 },
> +	{ V4L2_MBUS_FMT_RGB888_2X12_LE, 24 },
> +	{ V4L2_MBUS_FMT_ARGB8888_1X32, 32 },
> +	{ V4L2_MBUS_FMT_Y8_1X8, 8 },
> +	{ V4L2_MBUS_FMT_UV8_1X8, 8 },
> +	{ V4L2_MBUS_FMT_UYVY8_1_5X8, 40 },
> +	{ V4L2_MBUS_FMT_VYUY8_1_5X8, 40 },
> +	{ V4L2_MBUS_FMT_YUYV8_1_5X8, 40 },
> +	{ V4L2_MBUS_FMT_YVYU8_1_5X8, 40 },
> +	{ V4L2_MBUS_FMT_UYVY8_2X8, 16 },
> +	{ V4L2_MBUS_FMT_VYUY8_2X8, 16 },
> +	{ V4L2_MBUS_FMT_YUYV8_2X8, 16 },
> +	{ V4L2_MBUS_FMT_YVYU8_2X8, 16 },
> +	{ V4L2_MBUS_FMT_Y10_1X10, 10 },
> +	{ V4L2_MBUS_FMT_UYVY10_2X10, 20 },
> +	{ V4L2_MBUS_FMT_VYUY10_2X10, 20 },
> +	{ V4L2_MBUS_FMT_YUYV10_2X10, 20 },
> +	{ V4L2_MBUS_FMT_YVYU10_2X10, 20 },
> +	{ V4L2_MBUS_FMT_Y12_1X12, 12 },
> +	{ V4L2_MBUS_FMT_UYVY8_1X16, 16 },
> +	{ V4L2_MBUS_FMT_VYUY8_1X16, 16 },
> +	{ V4L2_MBUS_FMT_YUYV8_1X16, 16 },
> +	{ V4L2_MBUS_FMT_YVYU8_1X16, 16 },
> +	{ V4L2_MBUS_FMT_YDYUYDYV8_1X16, 16 },
> +	{ V4L2_MBUS_FMT_UYVY10_1X20, 20 },
> +	{ V4L2_MBUS_FMT_VYUY10_1X20, 20 },
> +	{ V4L2_MBUS_FMT_YUYV10_1X20, 20 },
> +	{ V4L2_MBUS_FMT_YVYU10_1X20, 20 },
> +	{ V4L2_MBUS_FMT_YUV10_1X30, 30 },
> +	{ V4L2_MBUS_FMT_AYUV8_1X32, 32 },
> +	{ V4L2_MBUS_FMT_UYVY12_2X12, 24 },
> +	{ V4L2_MBUS_FMT_VYUY12_2X12, 24 },
> +	{ V4L2_MBUS_FMT_YUYV12_2X12, 24 },
> +	{ V4L2_MBUS_FMT_YVYU12_2X12, 24 },
> +	{ V4L2_MBUS_FMT_UYVY12_1X24, 24 },
> +	{ V4L2_MBUS_FMT_VYUY12_1X24, 24 },
> +	{ V4L2_MBUS_FMT_YUYV12_1X24, 24 },
> +	{ V4L2_MBUS_FMT_YVYU12_1X24, 24 },
> +	{ V4L2_MBUS_FMT_SBGGR8_1X8, 8 },
> +	{ V4L2_MBUS_FMT_SGBRG8_1X8, 8 },
> +	{ V4L2_MBUS_FMT_SGRBG8_1X8, 8 },
> +	{ V4L2_MBUS_FMT_SRGGB8_1X8, 8 },
> +	{ V4L2_MBUS_FMT_SBGGR10_ALAW8_1X8, 8 },
> +	{ V4L2_MBUS_FMT_SGBRG10_ALAW8_1X8, 8 },
> +	{ V4L2_MBUS_FMT_SGRBG10_ALAW8_1X8, 8 },
> +	{ V4L2_MBUS_FMT_SRGGB10_ALAW8_1X8, 8 },
> +	{ V4L2_MBUS_FMT_SBGGR10_DPCM8_1X8, 8 },
> +	{ V4L2_MBUS_FMT_SGBRG10_DPCM8_1X8, 8 },
> +	{ V4L2_MBUS_FMT_SGRBG10_DPCM8_1X8, 8 },
> +	{ V4L2_MBUS_FMT_SRGGB10_DPCM8_1X8, 8 },
> +	{ V4L2_MBUS_FMT_SBGGR10_2X8_PADHI_BE, 16 },
> +	{ V4L2_MBUS_FMT_SBGGR10_2X8_PADHI_LE, 16 },
> +	{ V4L2_MBUS_FMT_SBGGR10_2X8_PADLO_BE, 16 },
> +	{ V4L2_MBUS_FMT_SBGGR10_2X8_PADLO_LE, 16 },
> +	{ V4L2_MBUS_FMT_SBGGR10_1X10, 10 },
> +	{ V4L2_MBUS_FMT_SGBRG10_1X10, 10 },
> +	{ V4L2_MBUS_FMT_SGRBG10_1X10, 10 },
> +	{ V4L2_MBUS_FMT_SRGGB10_1X10, 10 },
> +	{ V4L2_MBUS_FMT_SBGGR12_1X12, 24 },
> +	{ V4L2_MBUS_FMT_SGBRG12_1X12, 24 },
> +	{ V4L2_MBUS_FMT_SGRBG12_1X12, 24 },
> +	{ V4L2_MBUS_FMT_SRGGB12_1X12, 24 },
> +	{ V4L2_MBUS_FMT_JPEG_1X8, 8 },
> +	{ V4L2_MBUS_FMT_S5C_UYVY_JPEG_1X8, 8 },
> +	{ V4L2_MBUS_FMT_AHSV8888_1X32, 32 },
> +};
> +
> +}; /* namespace */
> +
>  /**
>   * \struct V4L2SubdeviceFormat
>   * \brief The V4L2 sub-device image format and sizes
> @@ -60,6 +147,14 @@ LOG_DECLARE_CATEGORY(V4L2)
>   * Section 4.15.3.1 of the above mentioned Linux kernel documentation section.
>   */
>  
> +/**
> + * \typedef V4L2SubdeviceFormat::infoMap
> + * \brief Map of static information associated with a V4L2 subdevice format
> + *
> + * \todo Expand with additional information. At the moment only the
> + * bits-per-pixel information is reported.
> + */
> +

And you can drop this too as the type doesn't need to be documented.
What we may document later is a format info structure that would contain
more than just the bpp, but there's no need to introduce that yet.

>  /**
>   * \var V4L2SubdeviceFormat::mbus_code
>   * \brief The image format bus code
> @@ -81,6 +176,24 @@ const std::string V4L2SubdeviceFormat::toString() const
>  	return ss.str();
>  }
>  
> +/**
> + * \brief Retrieve the number of bits per pixel for the V4L2 subdevice format
> + * \return The number of bits per pixel for the format, or default it to 8 if
> + * the format's mbus code is not supported

s/mbus/media bus/

> + */
> +uint8_t V4L2SubdeviceFormat::bitsPerPixel() const
> +{
> +	const auto it = formatInfoMap.find(mbus_code);
> +	if (it == formatInfoMap.end()) {
> +		LOG(V4L2, Error) << "No information available for format: '"

s/://

> +				 << toString() << "'";
> +		/* Return 8 to avoid divisions by 0. */
> +		return 8;

I think we should return 0 and check for this condition in the caller.
When we'll switch to a structure that will contain information about
formats, the formatInfo() function will return a pointer, which will be
null when the format is not known. I would prefer preparing the callers
for this already.

With these small changes,

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

> +	}
> +
> +	return it->second;
> +}
> +
>  /**
>   * \class V4L2Subdevice
>   * \brief A V4L2 subdevice as exposed by the Linux kernel

-- 
Regards,

Laurent Pinchart