libcamera: v4l2_videodevice: Match formats supported by the device

Now that V4L2PixelFormat::fromPixelFormat() returns a list of formats
to chose from by checking which ones are actually supported by the video
device.

The first format found to match one of the device supported ones is
returned.

As V4L2VideoDevice::toV4L2PixelFormat() is a const function which uses
other functions of the class, those functions has to be made const as
well.

In particular:

- enumPixelformats() and enumSizes() do not modify the class state and
  can safely be made const.
- formats() uses the above functions and does not itself modify the
  class state and can be made const
- add a const version of V4L2Device::ioctl() to be used by the now const
  functions

Signed-off-by: Jacopo Mondi <jacopo@jmondi.org>

2 files changed, 4 insertions, 3 deletions

diff --git a/include/libcamera/internal/v4l2_device.h b/include/libcamera/internal/v4l2_device.h
index a52a5f2c..f7ec3c70 100644
--- a/include/libcamera/internal/v4l2_device.h
+++ b/include/libcamera/internal/v4l2_device.h
@@ -55,6 +55,7 @@ protected:
 	int setFd(UniqueFD fd);
 
 	int ioctl(unsigned long request, void *argp);
+	int ioctl(unsigned long request, void *argp) const;
 
 	int fd() const { return fd_.get(); }
 
diff --git a/include/libcamera/internal/v4l2_videodevice.h b/include/libcamera/internal/v4l2_videodevice.h
index 29fa0bba..6d8850c9 100644
--- a/include/libcamera/internal/v4l2_videodevice.h
+++ b/include/libcamera/internal/v4l2_videodevice.h
@@ -205,7 +205,7 @@ public:
 	int getFormat(V4L2DeviceFormat *format);
 	int tryFormat(V4L2DeviceFormat *format);
 	int setFormat(V4L2DeviceFormat *format);
-	Formats formats(uint32_t code = 0);
+	Formats formats(uint32_t code = 0) const;
 
 	int setSelection(unsigned int target, Rectangle *rect);
 
@@ -251,8 +251,8 @@ private:
 	int getFormatSingleplane(V4L2DeviceFormat *format);
 	int trySetFormatSingleplane(V4L2DeviceFormat *format, bool set);
 
-	std::vector<V4L2PixelFormat> enumPixelformats(uint32_t code);
-	std::vector<SizeRange> enumSizes(V4L2PixelFormat pixelFormat);
+	std::vector<V4L2PixelFormat> enumPixelformats(uint32_t code) const;
+	std::vector<SizeRange> enumSizes(V4L2PixelFormat pixelFormat) const;
 
 	int requestBuffers(unsigned int count, enum v4l2_memory memoryType);
 	int createBuffers(unsigned int count,