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

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Date:	Thu, 22 Jul 2010 16:58:43 +0200
From:	Michał Nazarewicz <m.nazarewicz@...sung.com>
To:	Mark Brown <broonie@...nsource.wolfsonmicro.com>
Cc:	Marek Szyprowski <m.szyprowski@...sung.com>,
	'Daniel Walker' <dwalker@...eaurora.org>, linux-mm@...ck.org,
	Pawel Osciak <p.osciak@...sung.com>,
	'Xiaolin Zhang' <xiaolin.zhang@...el.com>,
	'Hiremath Vaibhav' <hvaibhav@...com>,
	'Robert Fekete' <robert.fekete@...ricsson.com>,
	'Marcus Lorentzon' <marcus.xm.lorentzon@...ricsson.com>,
	linux-kernel@...r.kernel.org,
	'Kyungmin Park' <kyungmin.park@...sung.com>,
	linux-arm-msm@...r.kernel.org
Subject: Re: [PATCH 2/4] mm: cma: Contiguous Memory Allocator added

On Thu, 22 Jul 2010 15:40:56 +0200, Mark Brown <broonie@...nsource.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.

-- 
Best regards,                                        _     _
| Humble Liege of Serenely Enlightened Majesty of  o' \,=./ `o
| Computer Science,  Michał "mina86" Nazarewicz       (o o)
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