[libcamera-devel] [PATCH v2] v4l2: v4l2_camera_proxy: Support MJPEG

[Paul Elder]

Add an entry for MJPEG in V4L2CameraProxy's PixelFormatInfo list to
allow proper calculation of sizeimage for MJPEG, such that the
parameters to mmap can align properly instead of failing. This allows
MJPEG to be used in the V4L2 compatibility layer.

Signed-off-by: Paul Elder <paul.elder at ideasonboard.com>
Reviewed-by: Niklas Söderlund <niklas.soderlund at ragnatech.se>

---
Changes in v2:
- add todo for better MJPEG sizeimage estimate
- update comment that the warning will only be printed if the set format
  has zero sizeimage at the time of reqbufs
---
 src/v4l2/v4l2_camera_proxy.cpp | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/src/v4l2/v4l2_camera_proxy.cpp b/src/v4l2/v4l2_camera_proxy.cpp
index 059f3cbe..07e746b4 100644
--- a/src/v4l2/v4l2_camera_proxy.cpp
+++ b/src/v4l2/v4l2_camera_proxy.cpp
@@ -358,8 +358,9 @@ int V4L2CameraProxy::vidioc_reqbufs(struct v4l2_requestbuffers *arg)
 	 * don't support streaming mmap. Since we don't support readwrite and
 	 * userptr either, the application will get confused and think that
 	 * we don't support anything.
-	 * On the other hand, if a format has a zero sizeimage (eg. MJPEG),
-	 * we'll get a floating point exception when we try to stream it.
+	 * On the other hand, if the set format at the time of reqbufs has a
+	 * zero sizeimage we'll get a floating point exception when we try to
+	 * stream it.
 	 */
 	if (sizeimage_ == 0)
 		LOG(V4L2Compat, Warning)
@@ -556,7 +557,7 @@ struct PixelFormatInfo {
 
 namespace {
 
-static const std::array<PixelFormatInfo, 13> pixelFormatInfo = {{
+static const std::array<PixelFormatInfo, 14> pixelFormatInfo = {{
 	/* RGB formats. */
 	{ PixelFormat(DRM_FORMAT_RGB888),	V4L2_PIX_FMT_BGR24,	1, {{ { 24, 1, 1 }, {  0, 0, 0 }, {  0, 0, 0 } }} },
 	{ PixelFormat(DRM_FORMAT_BGR888),	V4L2_PIX_FMT_RGB24,	1, {{ { 24, 1, 1 }, {  0, 0, 0 }, {  0, 0, 0 } }} },
@@ -573,6 +574,9 @@ static const std::array<PixelFormatInfo, 13> pixelFormatInfo = {{
 	{ PixelFormat(DRM_FORMAT_NV61),		V4L2_PIX_FMT_NV61,	2, {{ {  8, 1, 1 }, { 16, 2, 1 }, {  0, 0, 0 } }} },
 	{ PixelFormat(DRM_FORMAT_NV24),		V4L2_PIX_FMT_NV24,	2, {{ {  8, 1, 1 }, { 16, 2, 1 }, {  0, 0, 0 } }} },
 	{ PixelFormat(DRM_FORMAT_NV42),		V4L2_PIX_FMT_NV42,	2, {{ {  8, 1, 1 }, { 16, 1, 1 }, {  0, 0, 0 } }} },
+	/* Compressed formats. */
+	/* \todo Get better estimate from UVC device, via StreamConfiguration. */
+	{ PixelFormat(DRM_FORMAT_MJPEG),	V4L2_PIX_FMT_MJPEG,	1, {{ { 16, 1, 1 }, {  0, 0, 0 }, {  0, 0, 0 } }} },
 }};
 
 } /* namespace */
-- 
2.25.1