[libcamera-devel] [PATCH 2/4] v4l2: camera_proxy: Return correct type from VIDIOC_G_FMT

[Laurent Pinchart]

Hi Kieran,

On Mon, Jan 06, 2020 at 04:58:48PM +0000, Kieran Bingham wrote:
> On 06/01/2020 16:14, Laurent Pinchart wrote:
> > The VIDIOC_G_FMT implementation overwrites the v4l2_format type field
> > with 0. Fix it.
> 
> Could you clarify this please?
> 
> You mean the kernel changes the arg->type?
> 
> The whole function reads as:
> 
> int V4L2CameraProxy::vidioc_g_fmt(struct v4l2_format *arg)
> {
>         LOG(V4L2Compat, Debug) << "Servicing vidioc_g_fmt";
> 
>         if (!validateBufferType(arg->type))
>                 return -EINVAL;
> 
>         memset(&arg->fmt, 0, sizeof(arg->fmt));
> > +	arg->type = V4L2_BUF_TYPE_VIDEO_CAPTURE; /* LP-Addition */
>         arg->fmt.pix = curV4L2Format_.fmt.pix;
> 
>         return 0;
> }
> 
> 
> I see usage of arg->type in the validateBufferType before the memset.
> 
> Does this need to be set correctly before that ? or otherwise what is
> the purpose of the call to validateBufferType(arg->type)?

I meant that *our* implementation of VIDIOC_G_FMT unconditionally sets
arg->type to 0 (due to the memset). It's incorrect, the field should
retain its value. And now that I've written this, I realize that we only
memset arg->fmt, not arg... I'll drop this patch :-)

> > Signed-off-by: Laurent Pinchart <laurent.pinchart at ideasonboard.com>
> > ---
> >  src/v4l2/v4l2_camera_proxy.cpp | 1 +
> >  1 file changed, 1 insertion(+)
> > 
> > diff --git a/src/v4l2/v4l2_camera_proxy.cpp b/src/v4l2/v4l2_camera_proxy.cpp
> > index 2eeb12396d90..dd3ee3e6c6ff 100644
> > --- a/src/v4l2/v4l2_camera_proxy.cpp
> > +++ b/src/v4l2/v4l2_camera_proxy.cpp
> > @@ -229,6 +229,7 @@ int V4L2CameraProxy::vidioc_g_fmt(struct v4l2_format *arg)
> >  		return -EINVAL;
> >  
> >  	memset(&arg->fmt, 0, sizeof(arg->fmt));
> > +	arg->type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
> >  	arg->fmt.pix = curV4L2Format_.fmt.pix;
> >  
> >  	return 0;

-- 
Regards,

Laurent Pinchart