linux-kernel - Re: [PATCH, RFC] MIPS: jz4740: use dma filter function

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Message-ID: <yw1xtx04f54r.fsf@unicorn.mansr.com>
Date:	Tue, 06 Jan 2015 12:47:00 +0000
From:	Måns Rullgård <mans@...sr.com>
To:	Lars-Peter Clausen <lars@...afoo.de>
Cc:	Arnd Bergmann <arnd@...db.de>, linux-kernel@...r.kernel.org,
	Ralf Baechle <ralf@...ux-mips.org>, dmaengine@...r.kernel.org,
	alsa-devel@...a-project.org, linux-mmc@...r.kernel.org,
	linux-mips@...ux-mips.org
Subject: Re: [PATCH, RFC] MIPS: jz4740: use dma filter function

Lars-Peter Clausen <lars@...afoo.de> writes:

> On 01/05/2015 11:39 PM, Arnd Bergmann wrote:
>> As discussed on the topic of shmobile DMA today, jz4740 is the only
>> user of the slave_id field in dma_slave_config besides shmobile. This
>> use is really incompatible with the way that other drivers use the
>> dmaengine API, so we should get rid of it.
>
> Do you have a link to that discussion?
>
>>
>> This adds a trivial filter function that uses the filter param to
>> pass the dma type, and uses that in both drivers.
>
> In my opinion that's just from bad to worse. Using filter functions
> isn't that great in the first place. And using them to pass data from
> the consumer to the DMA provider is just a horrible abuse of the API.

It seems to me the only sane way to use the dmaengine API is in
conjunction with DT.

-- 
Måns Rullgård
mans@...sr.com
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