[libcamera-devel] [PATCH v2 4/4] libcamera: v4l2_videodevice: Warn if bytesused == 0 when queuing output buffer

[Laurent Pinchart]

Hi Umang,

On Wed, Oct 05, 2022 at 12:18:58PM +0530, Umang Jain wrote:
> On 10/5/22 3:59 AM, Laurent Pinchart via libcamera-devel wrote:
> > V4L2 has deprecated queuing output buffers with bytesused set to 0. Warn
> > if the caller attempts to do so.
> >
> > Signed-off-by: Laurent Pinchart <laurent.pinchart at ideasonboard.com>
> > ---
> >   src/libcamera/v4l2_videodevice.cpp | 5 +++++
> >   1 file changed, 5 insertions(+)
> >
> > diff --git a/src/libcamera/v4l2_videodevice.cpp b/src/libcamera/v4l2_videodevice.cpp
> > index 4d846f6be7fa..e30858c9fa02 100644
> > --- a/src/libcamera/v4l2_videodevice.cpp
> > +++ b/src/libcamera/v4l2_videodevice.cpp
> > @@ -1623,6 +1623,11 @@ int V4L2VideoDevice::queueBuffer(FrameBuffer *buffer)
> >   	if (V4L2_TYPE_IS_OUTPUT(buf.type)) {
> >   		const FrameMetadata &metadata = buffer->metadata();
> >   
> > +		for (const auto &plane : metadata.planes()) {
> > +			if (!plane.bytesused)
> > +				LOG(V4L2, Warning) << "byteused == 0 is deprecated";
> > +		}
> > +
> 
> Should the warning be printed depending on the kernel's version?

I don't think so. This behaviour has been deprecated in V4L2 for years,
and it will keep working for quite some time still. The goal of this
patch is to catch offenders in libcamera, to make sure pipeline handler
do the right thing going forward.

> As far as code is concerned,, it looks good to me.
> 
> Reviewed-by: Umang Jain <umang.jain at ideasonboard.com>
> 
> >   		if (numV4l2Planes != planes.size()) {
> >   			/*
> >   			 * If we have a multi-planar buffer with a V4L2

-- 
Regards,

Laurent Pinchart