linux-kernel - Re: [PATCH] kernel/dma: export dma_alloc_from

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Date:   Thu, 11 Jul 2019 12:03:32 +0200
From:   Christoph Hellwig <hch@....de>
To:     Robin Murphy <robin.murphy@....com>
Cc:     miles.chen@...iatek.com, Christoph Hellwig <hch@....de>,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        linux-kernel@...r.kernel.org, iommu@...ts.linux-foundation.org,
        wsd_upstream@...iatek.com, linux-mediatek@...ts.infradead.org
Subject: Re: [PATCH] kernel/dma: export dma_alloc_from_contiguous to modules

On Thu, Jul 11, 2019 at 09:50:58AM +0100, Robin Murphy wrote:
> On 11/07/2019 06:33, miles.chen@...iatek.com wrote:
>> From: Miles Chen <miles.chen@...iatek.com>
>>
>> This change exports dma_alloc_from_contiguous and
>> dma_release_from_contiguous to modules.
>>
>> Currently, we can add a reserve a memory node in dts files, make
>> it a CMA memory by setting compatible = "shared-dma-pool",
>> and setup the dev->cma_area by using of_reserved_mem_device_init_by_idx().
>>
>> Export dma_alloc_from_contiguous and dma_release_from_contiguous, so we
>> can allocate/free from/to dev->cma_area in kernel modules.
>
> As far as I understand, this was never intended for drivers to call 
> directly. If a device has its own private CMA area, then regular 
> dma_alloc_attrs() should allocate from that automatically; if that's not 
> happening already, then there's a bug somewhere.

Agreed.