Re: [V4l2-library] Messed up syscall return value

From: "H. Willstrand" <h.willstrand@gmail.com>
To: Jiri Slaby <jirislaby@gmail.com>
Cc: video4linux-list@redhat.com,
	v4l2 library <v4l2-library@linuxtv.org>,
	Brandon Philips <bphilips@suse.de>,
	SPCA50x Linux Device Driver Development
	<spca50x-devs@lists.sourceforge.net>
Subject: Re: [V4l2-library] Messed up syscall return value
Date: Tue, 29 Jul 2008 00:35:20 +0200	[thread overview]
Message-ID: <1217284520.3371.2.camel@localhost.localdomain> (raw)
In-Reply-To: <488E46BC.10104@gmail.com>

Hi!

I think the memory allocation is wrong, you have NBUFFERS = 2 but
memset( ... ) only allocates for 1 buffer.

Regards,
H.Willstrand

On Tue, 2008-07-29 at 00:22 +0200, Jiri Slaby wrote:
> On 07/29/2008 12:16 AM, Gregor Jasny wrote:
> > ioctl(3, VIDIOC_REQBUFS or VT_DISALLOCATE, 0x7fffbfda0060) = 2
> > 
> > Huh? Something evils seems to be going on in V4L2 land.
> > I've spotted the following lines in videobuf-core.c:videobuf_reqbufs
> > 
> >         req->count = retval;
> > 
> >  done:
> >         mutex_unlock(&q->vb_lock);
> >         return retval;
> > 
> > That would explain the retval '2'. It seems a retval = 0; statement is missing here for the success case.
> 
> Actually positive ioctl retval used to be often considered as OK in the past 
> (and this approach is still used in few char drivers).
> 
> But according to v4l docco, it isn't permitted here. Anyway I wouldn't place it 
> in videobuf-core.c, but in vivi code; letting this decision on Mauro (CCed) ;).
> 
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