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

Mike Frysinger vapier.adi at gmail.com
Wed Mar 11 18:36:38 CET 2009

On Fri, Jan 9, 2009 at 10:26, Rémi Denis-Courmont wrote:
> On Fri, 9 Jan 2009 13:21:34 +0100, Antoine Cellerier wrote:
>> On Fri, Jan 09, 2009, Mike Frysinger wrote:
>>> On Linux no-mmu systems, getting a shared mapping often results in
>>> failure. If the mmap() in v4l failed with MAP_SHARED, then fall back to
>> I'm not really sure how MAP_PRIVATE works. According to the man page it
>> creates a private copy on write mapping. Won't that mean that the
>> original memory area doesn't get updated?
> Yes. That's the whole point of MAP_PRIVATE - doing copy-on-write to not
> share your modifications with others.

which is why i made it a fallback.  attempting to use MAP_SHARED on a
nommu system results in a failure.  generally nommu does not have
multiple programs running simultaneously because it's an embedded
system, not a desktop, so only having one application run
simultaneously is the norm.

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