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Date: Fri, 17 Nov 2017 11:00:25 -0200
From: Mauro Carvalho Chehab <mchehab@osg.samsung.com>
To: Alexandre Courbot <acourbot@chromium.org>
Cc: Gustavo Padovan <gustavo@padovan.org>,
        <linux-media@vger.kernel.org>, Hans Verkuil <hverkuil@xs4all.nl>,
        Shuah Khan <shuahkh@osg.samsung.com>,
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        Gustavo Padovan <gustavo.padovan@collabora.com>
Subject: Re: [RFC v5 07/11] [media] vb2: add in-fence support to QBUF
Message-ID: <20171117110025.2a49db49@vento.lan>
In-Reply-To: <422c5326-374b-487f-9ef1-594f239438f1@chromium.org>
References: <20171115171057.17340-1-gustavo@padovan.org>
        <20171115171057.17340-8-gustavo@padovan.org>
        <422c5326-374b-487f-9ef1-594f239438f1@chromium.org>
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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.

-- 
Thanks,
Mauro