On 10/31/24 11:11, Laurent Pinchart wrote: > Hi Hans, > > Thank you for the patch. > > On Thu, Oct 31, 2024 at 08:50:04AM +0100, Hans Verkuil wrote: >> Clearly state that the V4L2_CID_MIN_BUFFERS_FOR_OUTPUT and >> V4L2_CID_MIN_BUFFERS_FOR_CAPTURE controls are required for >> stateful codecs. > > Wouldn't it be better for this kind of information to be centralized in > a stateful decoder document ? That would make it easier for developers > to see all they need to implement. Otherwise they would need to read > through the whole documentation to pick the parts of the API they need > to support in their drivers. It's also already mentioned in the documentation for the stateful de/encoders here: https://linuxtv.org/downloads/v4l-dvb-apis-new/userspace-api/v4l/dev-mem2mem.html Also, once this vicodec patch is merged: https://patchwork.linuxtv.org/project/linux-media/patch/1dd09050-40ca-4c5b-b985-819731140388@xxxxxxxxx/ I plan to push v4l2-compliance patches that explicitly test for the presence of these controls and fail if they are missing (like they are now in vicodec). Regards, Hans > >> Signed-off-by: Hans Verkuil <hverkuil@xxxxxxxxx> >> --- >> Documentation/userspace-api/media/v4l/control.rst | 6 ++++-- >> 1 file changed, 4 insertions(+), 2 deletions(-) >> >> diff --git a/Documentation/userspace-api/media/v4l/control.rst b/Documentation/userspace-api/media/v4l/control.rst >> index 57893814a1e5..9253cc946f02 100644 >> --- a/Documentation/userspace-api/media/v4l/control.rst >> +++ b/Documentation/userspace-api/media/v4l/control.rst >> @@ -290,13 +290,15 @@ Control IDs >> This is a read-only control that can be read by the application and >> used as a hint to determine the number of CAPTURE buffers to pass to >> REQBUFS. The value is the minimum number of CAPTURE buffers that is >> - necessary for hardware to work. >> + necessary for hardware to work. This control is required for stateful >> + decoders. >> >> ``V4L2_CID_MIN_BUFFERS_FOR_OUTPUT`` ``(integer)`` >> This is a read-only control that can be read by the application and >> used as a hint to determine the number of OUTPUT buffers to pass to >> REQBUFS. The value is the minimum number of OUTPUT buffers that is >> - necessary for hardware to work. >> + necessary for hardware to work. This control is required for stateful >> + encoders. >> >> .. _v4l2-alpha-component: >> >
