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Date: Wed, 28 Jul 2004 23:42:14 -0700
From: Andrew Morton <akpm@osdl.org>
To: Johannes Stezenbach <js@convergence.de>
Cc: viro@parcelfarce.linux.theplanet.co.uk, linux-kernel@vger.kernel.org
Subject: Re: 2.6.8-rc2-mm1
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Johannes Stezenbach <js@convergence.de> wrote:
>
> Andrew Morton wrote:
> > Johannes Stezenbach <js@convergence.de> wrote:
> > >
> > > This is a hack introduced by someone years ago. The "pointer" is
> > > actually an integer argument, e.g. in include/linux/dvb/audio.h:
> > > 
> > > #define AUDIO_SET_MUTE             _IO('o', 6)
> > > 
> > > actually takes an integer argument (!0 mute, 0 unmute), so one can write
> > > 
> > > 	if (ioctl(fd, AUDIO_SET_MUTE, 1) == -1)
> > > 		perror("mute");
> > 
> > Is it a boolean argument?
> > 
> > If so, we could change the code to do
> > 
> > 	parg = (void *)(arg ? 1 : 0);
> > 
> > so if someone dereferences it they'll get a nice oops.
> 
> Unfortunately there are a few more ioctls which use enums,
> e.g. AUDIO_CHANNEL_SELECT has an argument of type
> audio_channel_select_t etc. (yes, I know, those typedefs
> should go). Or even DMX_SET_BUFFER_SIZE...

OK.  Well how's about we add a fifth argument to that callback function, of
type `int'?  Stick this integer in there and leave the fourth argument NULL
for this class of ioctl?