Re: [ANN] Request for Topics and registration for a Media Summit September 16th

[Laurent Pinchart <laurent.pinchart@ideasonboard.com>]

Hi Mauro,

On Wed, Jun 12, 2024 at 10:44:06PM +0200, Mauro Carvalho Chehab wrote:
> Em Wed, 12 Jun 2024 11:34:30 +0300 Laurent Pinchart escreveu:
> 
> > Focussing on this topic, if we're brainstorming memory management for
> > media devices, I'd like to throw in a controversial idea. In addition to
> > being clearer on the fact that USERPTR is deprecated, I would like to
> > deprecate MMAP too and only focus on DMABUF. I believe Linux needs a
> > centralized buffer allocator, instead of having multiple allocation APIs
> > scattered in different places. There are design ideas in gralloc that we
> > could benefit from.
> 
> Deprecating USERPTR is doable, as not many apps use it, and they're
> mostly focused on complex camera/ARM scenario. Now, deprecating MMAP at 
> V4L2 core is a different history: lots of different userspace programs,
> including browsers and proprietary apps like zoom, etc. rely on MMAP
> support. We can only consider deprecating MMAP once applications switch 
> to DMABUF.

Deprecating doesn't mean dropping it right away, it means telling
application developers that DMABUF is the recommended way. We will still
have to support MMAP for a long time, including fixing bugs in it, as
that will be a long transition. And it first requires solving the
problem of centralizing allocation for DMABUF. It won't happen
overnight, but I'm trying to gather support for the idea, and get people
to collaborate on solving the technical problems that are currently
blocking this long term evolution. If the media subsystem endorsed the
effort, basically saying publicly that we are fine deprecating MMAP in
principle once a good replacement will be available, it may help. I
don't expect the deprecation to happen before at least two years, and
the removal from the kernel would probably take another 10 to 15 years
:-)

-- 
Regards,

Laurent Pinchart