libcamera: Define constants for pixel formats in the public API

libcamera uses pixel format FourCC and modifier values from DRM. This
requires inclusion of drm_fourcc.h, creating a dependency on a header
that is packaged differently between distributions, and causing possible
issues with third-party applications.

Define constants for the supported pixel formats in the new formats.h
public API header, in order to remove the dependency on drm_fourcc.h.
The header is generated by a Python script from a list of supported
formats. The numerical values for the FourCC and modifier are extracted
from drm_fourcc.h by the script, ensuring that numerical values are not
inadvertently modified and preserving the direct interoperability.

The pixel formats constants can't be generated solely from drm_fourcc.h,
as that header defines FourCC values and modifier values, but doesn't
list the valid combinations. The supported formats are thus stored in a
YAML file, which contains the FourCC and optional modifier for each
supported format. We may later extend the YAML file to include formats
documentation, and possibly formats metadata to populate the
pixelFormatInfo map (in formats.cpp) automatically.

Now that two formats.h header are present (one in include/libcamera/ and
one in include/libcamera/internal/), we need to explicitly qualify the
Doxygen \file directive with a path.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Niklas Söderlund <niklas.soderlund@ragnatech.se>
Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com>

1 files changed, 3 insertions, 1 deletions

diff --git a/src/libcamera/pixel_format.cpp b/src/libcamera/pixel_format.cpp
index d501c5f0..f191851a 100644
--- a/src/libcamera/pixel_format.cpp
+++ b/src/libcamera/pixel_format.cpp
@@ -5,6 +5,7 @@
  * pixel_format.cpp - libcamera Pixel Format
  */
 
+#include <libcamera/formats.h>
 #include <libcamera/pixel_format.h>
 
 /**
@@ -21,7 +22,8 @@ namespace libcamera {
  * The PixelFormat type describes the format of images in the public libcamera
  * API. It stores a FourCC value as a 32-bit unsigned integer and a modifier.
  * The FourCC and modifier values are defined in the Linux kernel DRM/KMS API
- * (see linux/drm_fourcc.h).
+ * (see linux/drm_fourcc.h). Constant expressions for all pixel formats
+ * supported by libcamera are available in libcamera/formats.h.
  */
 
 /**