v4l2: v4l2_compat: Add V4L2 compatibility layer

Add libcamera V4L2 compatibility layer.

This initial implementation supports the minimal set of V4L2 operations,
which allows getting, setting, and enumerating formats, and streaming
frames from a video device. Some data about the wrapped V4L2 video
device are hardcoded.

Add a build option named 'v4l2' and adjust the build system to
selectively compile the V4L2 compatibility layer.

For now we match the V4L2 device node to a libcamera camera based on a
devnum that a pipeline handler may optionally map to a libcamera
camera.

Signed-off-by: Paul Elder <paul.elder@ideasonboard.com>
Reviewed-by: Jacopo Mondi <jacopo@jmondi.org>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>

1 files changed, 4 insertions, 0 deletions

diff --git a/src/meson.build b/src/meson.build
index 67ad20aa..5adcd61f 100644
--- a/src/meson.build
+++ b/src/meson.build
@@ -6,3 +6,7 @@ subdir('libcamera')
 subdir('ipa')
 subdir('cam')
 subdir('qcam')
+
+if get_option('v4l2')
+    subdir('v4l2')
+endif