[libcamera-devel] [PATCH v2 0/7] Introduce formats:: namespace for libcamera pixel formats

[scerveau]

Hello Laurent,

Yesterday I tried a different approach from previous attempt, where I 
proposed to install the libdrm headers in libcamera include folders.

Indeed I succeeded to make libcamera compile without including 
drm_fourcc.h in pixel_format.h, see attached patches.

This is building correctly on my machine (ubuntu 18.04) with a simple 
`meson build`. But I might have missed use cases.

Concerning the libdrm dependency or includes, I haven't noticed with 
Debian/Buster or ArchLinux/latest (docker images) any issue mentioned 
with libdrm include folder. Both can be found with pkg-config on Ubuntu 
as well.

On the other hand your approach might be better, to remove the 
dependency to libdrm and create your own define for the format if it's 
going to be the only dependency, the project will have to libdrm.

But in this case the patch is missing to remove those files then:

- drm.h
- drm_fourcc.h
- drm_mode.h

Stéphane.




On 10/6/20 1:23, Laurent Pinchart wrote:
> Hello,
> 
> This patch series is an attempt to fix a problem caused by a direct
> dependency on drm_fourcc.h in the libcamera public API.
> 
> libcamera specifies pixel formats using the DRM pixel format FourCC and
> modifiers. This requires both internal code and applications to include
> drm_fourcc.h. For internal code, we carry a copy of the header to avoid
> external dependencies. For third-party applications, however,
> drm_fourcc.h needs to be accessible from system includes. It turns out
> that the file is shipped by two different packages:
> 
> - libdrm, which typically installs it in /usr/include/libdrm/
> - kernel headers or libc headers, which typically installs it in
>    /usr/include/drm
> 
> We don't want to make libdrm a dependency for applications using
> libcamera. Unfortunately, depending on drm_fourcc.h being provided by
> the distribution kernel headers or libc headers package causes issues,
> as not all distributions install the header in /usr/include/drm/. Ubuntu
> and Gentoo do, but Debian and Arch don't.
> 
> The best option may be to remove the dependency on the macros provided
> by drm_fourcc.h, while keeping the pixel format numerical values
> identical. This is what this patch series attempts to do.
> 
> Patch 1/7 creates a new libcamera::formats:: namespace and populates it
> with constants (in the form of constexpr) for all supported pixel
> formats. The values are automatically generated from a list of formats,
> stored in formats.yaml, and the numerical values for the DRM FourCCs and
> modifiers are extracted from drm_fourcc.h.
> 
> Patches 2/7 to 7/8 then replace usage of the DRM_FORMAT_* macros through
> the code.
> 
> Laurent Pinchart (7):
>    libcamera: Define constants for pixel formats in the public API
>    gst: Replace explicit DRM FourCCs with libcamera formats
>    qcam: Replace explicit DRM FourCCs with libcamera formats
>    v4l2: Replace explicit DRM FourCCs with libcamera formats
>    test: Replace explicit DRM FourCCs with libcamera formats
>    libcamera: pipeline: Replace explicit DRM FourCCs with libcamera
>      formats
>    libcamera: Replace explicit DRM FourCCs with libcamera formats
> 
>   include/libcamera/formats.h.in                |  44 ++++++
>   include/libcamera/gen-formats.py              | 118 ++++++++++++++
>   include/libcamera/meson.build                 |  22 +++
>   include/libcamera/pixel_format.h              |   2 -
>   src/android/camera_device.cpp                 |   9 +-
>   src/gstreamer/gstlibcamera-utils.cpp          |  62 ++++----
>   src/libcamera/formats.cpp                     | 148 +++++++++---------
>   src/libcamera/formats.yaml                    | 124 +++++++++++++++
>   src/libcamera/pipeline/ipu3/ipu3.cpp          |  16 +-
>   .../pipeline/raspberrypi/raspberrypi.cpp      |  10 +-
>   src/libcamera/pipeline/rkisp1/rkisp1.cpp      |  19 +--
>   src/libcamera/pipeline/vimc/vimc.cpp          |  11 +-
>   src/libcamera/pixel_format.cpp                |   4 +-
>   src/libcamera/v4l2_pixelformat.cpp            |  83 +++++-----
>   src/qcam/dng_writer.cpp                       |  17 +-
>   src/qcam/format_converter.cpp                 |  36 +++--
>   src/qcam/viewfinder.cpp                       |  10 +-
>   src/v4l2/v4l2_camera_proxy.cpp                |  29 ++--
>   test/v4l2_videodevice/buffer_cache.cpp        |   3 +-
>   19 files changed, 540 insertions(+), 227 deletions(-)
>   create mode 100644 include/libcamera/formats.h.in
>   create mode 100755 include/libcamera/gen-formats.py
>   create mode 100644 src/libcamera/formats.yaml
> 
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