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SubjectRe: [RFC v5 07/11] [media] vb2: add in-fence support to QBUF
2017-11-17 Mauro Carvalho Chehab <mchehab@osg.samsung.com>:

> Em Fri, 17 Nov 2017 15:49:23 +0900
> Alexandre Courbot <acourbot@chromium.org> escreveu:
>
> > > @@ -178,6 +179,12 @@ static int vb2_queue_or_prepare_buf(struct
> > > vb2_queue *q, struct v4l2_buffer *b,
> > > return -EINVAL;
> > > }
> > >
> > > + if ((b->fence_fd != 0 && b->fence_fd != -1) &&
> >
> > Why do we need to consider both values invalid? Can 0 ever be a valid fence
> > fd?
>
> Programs that don't use fences will initialize reserved2/fence_fd field
> at the uAPI call to zero.
>
> So, I guess using fd=0 here could be a problem. Anyway, I would, instead,
> do:
>
> if ((b->fence_fd < 1) &&
> ...
>
> as other negative values are likely invalid as well.

We are checking when the fence_fd is set but the flag wasn't. Checking
for < 1 is exactly the opposite. so we keep as is or do it fence_fd > 0.

Gustavo

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