Re: Announcing libv4l 0.3.1 aka "the vlc release"

From: Gregor Jasny <jasny@vidsoft.de>
To: Hans de Goede <j.w.r.degoede@hhs.nl>
Cc: video4linux-list@redhat.com, v4l2 library <v4l2-library@linuxtv.org>
Subject: Re: Announcing libv4l 0.3.1 aka "the vlc release"
Date: Thu, 3 Jul 2008 22:36:23 +0200	[thread overview]
Message-ID: <20080703203623.GI18818@vidsoft.de> (raw)
In-Reply-To: <4867F380.1040803@hhs.nl>

Hi,

I've just included libv4l2 in our app. After after a short debugging
session I noticed the following:

In the man page the ioctl prototype is defined as
int ioctl(int d, int request, ...). To catch the EINTR case I wrote a
wrapper function:

int xioctl (int fd, int request, void *arg)

But as long as the request argument is int instead of unsigned long, the
request gets sign extended:

xioctl (fd, VIDIOC_TRY_FMT, &fmt)
(gdb) p/x request
$2 = 0xc0d05640

int v4l2_ioctl (int fd, unsigned long int request, ...);
(gdb) p/x request
$3 = 0xffffffffc0d05640

Maybe you should mention this "issue" in the FAQ or documentaion.

Cheers,
Gregor

PS: Should I submit the sar-constraint patch to Thierry myself?

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