Graphics memory management in ARM/Embedded Linux

[Tom Cooksey]

2011/4/20 microcai <microcai at fedoraproject.org>

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> 于 2011年04月20日 20:39, Tom Cooksey 写道:
> > Hi All,
> >
> > Please excuse the spam... just trying to spread the word: Linaro is
> > currently developing a graphics memory manager for Linux which allows
> > buffers to be shared between different devices and different processes.
> On
> > ARM SoCs, many different hw devices need to access the same buffer (which
> > E.g. GEM doesn't support). As a simple example, a GPU needs to write to a
> > buffer which a display controller reads from. At least in ARM-Linux land,
> > this is a fairly hot-topic and a dedicated mailing list has been created
> to
> > discuss different requirements, figure out if TTM/GEM can be adapted,
> etc.
> >
> >
> > The mailing list is here:
> >
> > http://lists.linaro.org/mailman/listinfo/linaro-mm-sig
> >
> >
> > There's also a wiki page gathering requirements here:
> >
> >
> https://wiki.linaro.org/WorkingGroups/Middleware/Graphics/Projects/UnifiedMemoryManagement
> >
> >
> > Hopefully there's people on the Wayland list which this will be
> interesting
> > to. Would be cool if a Wayland compositor used the mechanism Linaro comes
> up
> > with to share window buffers between different processes!
> >
> >
> >
> > Cheers,
> >
> > Tom
> >
> >
> >
>
> Not again, due!
> Does DRI has some mentally wrong that cann't be fixed other than re-create?
>

Yes, possibly. The existing memory managers in Linux (GEM & TTM) don't:

a) Allow buffers to be shared between different device drivers
b) Don't allow physically contiguous memory allocations (something simple
hardware without MMUs need)

So while I agree re-inventing something just for the sake of it is bad,
that's not what's happening. In fact, I think there's a good chance TTM will
be ripped out, stuck into its own driver (with its own device node /dev/ttm)
and extended to meet everyone's requirements. At least there has been some
feasibility work done by Dave Airlie to partially address issue (a):
http://airlied.livejournal.com/71734.html.


Cheers,

Tom
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