On Sun, Feb 02, 2014 at 11:21:13AM +0100, Laurent Pinchart wrote:
> Hi Hans,
>
> On Friday 31 January 2014 09:43:00 Hans Verkuil wrote:
> > I think you might want to add a check in uvc_queue_setup to verify the
> > fmt that create_bufs passes. The spec says that: "Unsupported formats
> > will result in an error". In this case I guess that the format basically
> > should match the current selected format.
> >
> > I'm unhappy with the current implementations of create_bufs (see also this
> > patch:
> > http://www.mail-archive.com/linux-media@vger.kernel.org/msg70796.html).
> >
> > Nobody is actually checking the format today, which isn't good.
> >
> > The fact that the spec says that the fmt field isn't changed by the driver
> > isn't helping as it invalidated my patch from above, although that can be
> > fixed.
> >
> > I need to think about this some more, but for this particular case you can
> > just do a memcmp of the v4l2_pix_format against the currently selected
> > format and return an error if they differ. Unless you want to support
> > different buffer sizes as well?
>
> Isn't the whole point of VIDIOC_CREATE_BUFS being able to create buffers of
> different resolutions than the current active resolution ?
For that to work the driver in question would need to keep track of per-buffer
format and resolution, and not only of per-queue format and resolution.
For now, would something like the following be enough? Unfortunately the uvc
driver doesn't keep a v4l2_format around that we could just memcmp against:
diff --git a/drivers/media/usb/uvc/uvc_v4l2.c b/drivers/media/usb/uvc/uvc_v4l2.c
index fa58131..7fa469b 100644
--- a/drivers/media/usb/uvc/uvc_v4l2.c
+++ b/drivers/media/usb/uvc/uvc_v4l2.c
@@ -1003,10 +1003,26 @@ static long uvc_v4l2_do_ioctl(struct file *file,
unsigned int cmd, void *arg)
case VIDIOC_CREATE_BUFS:
{
struct v4l2_create_buffers *cb = arg;
+ struct v4l2_pix_format *pix;
+ struct uvc_format *format;
+ struct uvc_frame *frame;
if (!uvc_has_privileges(handle))
return -EBUSY;
+ format = stream->cur_format;
+ frame = stream->cur_frame;
+ pix = &cb->format.fmt.pix;
+
+ if (pix->pixelformat != format->fcc ||
+ pix->width != frame->wWidth ||
+ pix->height != frame->wHeight ||
+ pix->field != V4L2_FIELD_NONE ||
+ pix->bytesperline != format->bpp * frame->wWidth / 8 ||
+ pix->sizeimage != stream->ctrl.dwMaxVideoFrameSize ||
+ pix->colorspace != format->colorspace)
+ return -EINVAL;
+
return uvc_create_buffers(&stream->queue, cb);
}
regards
Philipp
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