linux-kernel - Re: [PATCH 06/13] DMAENGINE: driver for the ARM PL080/PL081 PrimeCells

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Date:	Thu, 23 Dec 2010 00:10:12 +0000
From:	Russell King - ARM Linux <linux@....linux.org.uk>
To:	Dan Williams <dan.j.williams@...el.com>
Cc:	Linus Walleij <linus.walleij@...ricsson.com>,
	Viresh Kumar <viresh.kumar@...com>,
	Kukjin Kim <kgene.kim@...sung.com>, yuanyabin1978@...a.com,
	linux-kernel@...r.kernel.org, Ben Dooks <ben-linux@...ff.org>,
	Peter Pearse <peter.pearse@....com>,
	linux-arm-kernel@...ts.infradead.org,
	Alessandro Rubini <rubini@...pv.it>
Subject: Re: [PATCH 06/13] DMAENGINE: driver for the ARM PL080/PL081
	PrimeCells

On Wed, Dec 22, 2010 at 03:45:39PM -0800, Dan Williams wrote:
> 3.6 Constraints:
> 1/ Calls to async_<operation> are not permitted in IRQ context.  Other
>    contexts are permitted provided constraint #2 is not violated.

BTW, this is misleading.  Have the functions been renamed dma_async_xxx(),
eg dma_async_memcpy_buf_to_buf etc, or are you referring just to:

	async_dmaengine_get
	async_dmaengine_put
	async_dma_find_channel
	async_dma_find_channel
	async_tx_ack
	async_tx_clear_ack
	async_tx_test_ack

Beware of just renaming it to dma_async_<operation> as there's other
functions in that namespace which may not be appropriate.

Eg, is it really illegal to issue call dma_async_issue_pending() from
IRQ context?  That'd make it exceedingly difficult to use the DMA
engine with the slave API in a lot of device drivers.
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