linux-kernel - Re: DMA APIs gumble grumble

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Date:	Wed, 8 Nov 2006 10:25:36 +0200
From:	Muli Ben-Yehuda <muli@...ibm.com>
To:	Benjamin Herrenschmidt <benh@...nel.crashing.org>
Cc:	linux-input@...ey.karlin.mff.cuni.cz,
	Linux Kernel list <linux-kernel@...r.kernel.org>,
	"David S. Miller" <davem@...emloft.net>,
	Paul Mackerras <paulus@...ba.org>,
	Anton Blanchard <anton@...ba.org>, Greg KH <greg@...ah.com>
Subject: Re: DMA APIs gumble grumble

On Wed, Nov 08, 2006 at 12:54:37PM +1100, Benjamin Herrenschmidt wrote:

>  - For platforms like powerpc where I can have multiple busses on
> different IOMMU's and with possibly different DMA ops, I really need to
> have a per-device data structure for use by the DMA ops (in fact, in my
> case, containing the DMA ops themselves). Right now, I defined a notion
> of "device extension" (struct device_ext) that my current implementation
> puts in device->firmware_data (don't look for it upstream, it's all
> patches queuing up for 2.6.20 and about to go into powerpc.git), but
> that I'd like to have flat in struct device instead. Would it be agreed
> that linux/device.h includes itself an asm/device.h which contains a
> definition for a struct device_ext that is within struct device ? That
> would also avoid a pointer indirection which is a good thing for DMA
> operations

I want multiple dma_ops for Calgary on x86-64, so strong thumbs up for
doing this in a generic manner. device_ext kinda sucks as a name,
though... if it's used for just dma_ops, how about device_dma_ops?

I agree with the rest of your suggestions too, FWIW.

Cheers,
Muli
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