[vlc-devel] [PATCH] v4l/v4l2: add mmap() fall back for nommu systems

[Rémi Denis-Courmont]

On Wed, 01 Apr 2009 18:18:17 +0200, Rémi Denis-Courmont <remi at remlab.net>
wrote:
> 
> On Sun, 15 Mar 2009 04:27:13 -0400, Mike Frysinger <vapier.adi at gmail.com>
> wrote:
>> i imagine the nommu kernel code simply lies.  we know it works because
>> we've used v4l on a nommu system.  we have vlc capture via v4l from a
>> black & white sensor and stream it via rtp across the network to a
>> desktop system.
> 
> I am not so convinced that it works properly on a MMU system, as it is
> specification-wise incorrect. And mmap() can fail for other reasons than
> "there is no MMU and you asked for a private copy".

Err, I meant non-private. In fact, it really makes no sense that this
fails. I can see why no-MMU would make MAP_PRIVATE not to work, but I do
not see what's wrong with MAP_SHARED. In the latter case, the driver can
simply return the physical memory location to all users, no?

-- 
Rémi Denis-Courmont