linux-kernel - Re: [spi-devel-general] [Patch] Add spi full duplex mode transfer support

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Message-Id: <200608300926.32532.david-b@pacbell.net>
Date:	Wed, 30 Aug 2006 09:26:31 -0700
From:	David Brownell <david-b@...bell.net>
To:	stephen@...eetfiresound.com
Cc:	Manish Jaggi <manish.jaggi@...il.com>,
	spi-devel-general@...ts.sourceforge.net,
	Luke Yang <luke.adi@...il.com>, linux-kernel@...r.kernel.org
Subject: Re: [spi-devel-general] [Patch] Add spi full duplex mode transfer support

On Wednesday 30 August 2006 8:56 am, Stephen Street wrote:

> My experiance has shown the most stack allocated transfer buffers are
> not 8 byte aligned and thus use PIO mode.

Of course, providing a transfer buffer on the stack is nonportable;
it's not DMA-safe (especially on systems with dma-incoherent caches!),
while transfer buffers are required to be DMA-safe so that controller
buffers can choose to use DMA for _all_ transfers if they want.

- Dave

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