linux-kernel - Re: [PATCH] CMA: Don't return a valid cma for non-cma dev

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Message-ID: <20150805104627.GB27241@shbuild888>
Date:	Wed, 5 Aug 2015 18:46:27 +0800
From:	Feng Tang <feng.tang@...el.com>
To:	Michal Nazarewicz <mina86@...a86.com>
Cc:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"m.szyprowski@...sung.com" <m.szyprowski@...sung.com>,
	"kyungmin.park@...sung.com" <kyungmin.park@...sung.com>,
	"akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
	"iamjoonsoo.kim@....com" <iamjoonsoo.kim@....com>,
	"john.stultz@...aro.org" <john.stultz@...aro.org>
Subject: Re: [PATCH] CMA: Don't return a valid cma for non-cma dev

On Wed, Aug 05, 2015 at 12:28:03PM +0200, Michal Nazarewicz wrote:
> On Wed, Aug 05 2015, Feng Tang wrote:
> > that for a system which needs multiple cma heaps (like for security
> > reason), they may have to share one struct device *dev, as in
> > ion_cma_heap_create()
> 
> If you need several CMA areas to allocate from, create multiple struct
> devices.

Yes, that's my thought too. The normal cma case for SOCs are one platform
device is created in drivers/staging/android/ion/xxx_ion.c, then that
device's pointer will be transferred into ion_cma_heap_create() inside
of the struct ion_platform_heap data.

And it's not easy to create multiple platform devices. And it may be
better to give each cma_heap one dedicated device in struct ion_cma_heap
which could be used as a parameter for 
	dma_alloc_from_contigous() --> cma_alloc()

Thanks,
Feng
 
> -- 
> Best regards,                                         _     _
> .o. | Liege of Serenely Enlightened Majesty of      o' \,=./ `o
> ..o | Computer Science,  Michał “mina86” Nazarewicz    (o o)
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