[Linaro-mm-sig] Memory Management Discussion

[Jordan Crouse]

On 04/20/2011 12:55 AM, Daniel Vetter wrote:
> On Wed, Apr 20, 2011 at 8:25 AM, Arnd Bergmann<arnd at arndb.de>  wrote:
>> On Wednesday 20 April 2011 03:52:53 Clark, Rob wrote:
>>>  From DRI perspective.. I guess the global buffer name is restricted to
>>> a 4 byte integer, unless you change the DRI proto..
>>
>> I still like the idea of using file handles to pass the buffers between
>> kernel subsystems. Maybe there could be an ioctl to encapsulate a buffer
>> from DRI in a file so we can give it to another subsystem, and/or an
>> ioctl to register a buffer from a file handle with DRI.
>
> That's been the original design of gem, i.e. using fd handles (and perhaps even
> passing them around in unix domain sockets). There's one small problem with
> that approach: You're quickly running out of fds with the linux default limit of
> 1024. Hence the roll-your-own approach.
>
> Aside: I'll be participating as a gem drm/i915 hacker. I'll send a
> short overview
> of how gem/kms tackles these problems after easter because our approach is
> rather different from what the arm community seems to want (as far as I can
> tell).

I don't think the goals and aspirations of both APIs are really that different when you
get down to it. I think the biggest concern that most ARM vendors have is that GEM is tied
to DRM and KMS in spirit, and DRM/KMS/GEM as a whole is pretty scary.  If you look at any
one of our implementations the GEM wheel gets re-invented a lot, so there is a lot of overlap
and a chance to collaborate.

Jordan