Re: [PATCH 2/4] mm: cma: Contiguous Memory Allocator added

["Michał Nazarewicz" <m.nazarewicz@samsung.com>]

On Thu, 22 Jul 2010 15:40:56 +0200, Mark Brown <broonie@opensource.wolfsonmicro.com> wrote:

> On Thu, Jul 22, 2010 at 03:24:26PM +0200, Michał Nazarewicz wrote:
>
>> That's why command line is only intended as a way to overwrite the
>> defaults which are provided by the platform.  In a final product,
>> configuration should be specified in platform code and not on
>> command line.
>
> Yeah, agreed though I'm not convinced we can't do it via userspace
> (initrd would give us a chance to do stuff early) or just kernel
> rebuilds.

If there's any other easy way of overwriting platform's default I'm happy
to listen. :)

>> >It sounds like apart from the way you're passing the configuration in
>> >you're doing roughly what I'd suggest.  I'd expect that in a lot of
>> >cases the map could be satisfied from the default region so there'd be
>> >no need to explicitly set one up.
>
>> Platform can specify something like:
>
>> 	cma_defaults("reg=20M", "*/*=reg");
>
>> which would make all the drivers share 20 MiB region by default.
>
> Yes, exactly - probably you can even have a default region backed by
> normal vmalloc() RAM which would at least be able to take a stab at
> working by default.

Not sure what you mean here.  vmalloc() allocated buffers cannot be used
with CMA since they are not contiguous in memory.

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