Message-ID: <4DF782F1.9030105@codeaurora.org>
Date: Tue, 14 Jun 2011 09:49:05 -0600
From: Jordan Crouse <jcrouse@codeaurora.org>
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To: Alan Cox <alan@lxorguk.ukuu.org.uk>
CC: Marek Szyprowski <m.szyprowski@samsung.com>,
        "'Ankita Garg'" <ankita@in.ibm.com>,
        "'Daniel Walker'" <dwalker@codeaurora.org>,
        "'Arnd Bergmann'" <arnd@arndb.de>,
        "'Johan MOSSBERG'" <johan.xx.mossberg@stericsson.com>,
        "'Jesse Barker'" <jesse.barker@linaro.org>,
        "'Mel Gorman'" <mel@csn.ul.ie>, linux-kernel@vger.kernel.org,
        "'Michal Nazarewicz'" <mina86@mina86.com>,
        linaro-mm-sig@lists.linaro.org, linux-mm@kvack.org,
        "'Kyungmin Park'" <kyungmin.park@samsung.com>,
        "'KAMEZAWA Hiroyuki'" <kamezawa.hiroyu@jp.fujitsu.com>,
        "'Andrew Morton'" <akpm@linux-foundation.org>,
        linux-arm-kernel@lists.infradead.org, linux-media@vger.kernel.org
Subject: Re: [Linaro-mm-sig] [PATCH 02/10] lib: genalloc: Generic allocator
 improvements
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On 06/10/2011 06:52 AM, Alan Cox wrote:
>> I plan to replace it with lib/bitmap.c bitmap_* based allocator (similar like
>> it it is used by dma_declare_coherent_memory() and friends in
>> drivers/base/dma-coherent.c). We need something really simple for CMA area
>> management.
>>
>> IMHO allocate_resource and friends a bit too heavy here, but good to know
>> that such allocator also exists.
>
> Not sure I'd class allocate_resource as heavyweight but providing it's
> using something that already exists rather than inventing yet another
> allocator.
>
> This wants dealing with before it goes upstream though so the chaneges in
> lib/*c etc never have to reach mainline and then get changed back.

Even if CMA doesn't end up using genalloc, there are existing consumers of
the API and I think the _aligned function has value.

I agree that allocate_resource isn't overly heavy, but comparatively genalloc
is really simple and lightweight for a driver to manage a contiguous address
space without a lot of extra thought. I think both APIs serve slightly
different masters, but if somebody thought about it long enough there could
be some consolidation (same goes for the internal guts of
dma_declare_coherent_memory).

I agree with Michal - if genalloc goes deprecated, then so be it, but as
long as it lives, I think its useful to get these functions upstream.

Jordan
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