linux-kernel - Re: [PATCH] arm: dma-mapping: move consistent_init to early

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Date:	Fri, 17 Dec 2010 15:14:35 -0800 (PST)
From:	"Saravana Kannan" <skannan@...eaurora.org>
To:	"Catalin Marinas" <catalin.marinas@....com>
Cc:	"Saravana Kannan" <skannan@...eaurora.org>,
	"Russell King - ARM Linux" <linux@....linux.org.uk>,
	dwalker@...eaurora.org, linux-arm-msm@...r.kernel.org,
	"Nicolas Pitre" <nico@...vell.com>, linux-kernel@...r.kernel.org,
	"Jeff Ohlstein" <johlstei@...eaurora.org>,
	"Tejun Heo" <tj@...nel.org>, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH] arm: dma-mapping: move consistent_init to 
     early_initcall

Catalin Marinas wrote:
>> Russell,
>>
>> I agree with your point about using an API for purpose and not property.
>> But I read Catalin's proposal as, let's treat secure domain as another
>> DMA
>> "device". If we make a conscious agreement to do that, then using the
>> DMA
>> API for secure domain would be "using it for its purpose" and we will
>> make
>> an effort to not break it with future updates. Of course, if we don't
>> agree on that proposal, then we can't use the DMA API for secure domain
>> stuff.
>
> If there is no better proposal, I'm for such extension to the DMA API.
> From the kernel perspecitve, the secure side is just another entity
> that accesses the RAM directly. It's not a physically separate device
> indeed but from a direct memory access perspective it can be treated
> as any other device.
>
> In the DMA API we can fall back to the non-coherent ops when a NULL
> struct device is passed. I assume in your code you already pass a NULL
> device to dma_alloc_coherent().

Russell,

Would the extension of the DMA API as described above be acceptable to
you? If not, can you please suggest an alternative that's acceptable to
you?

-Saravana
-- 
Sent by an employee of the Qualcomm Innovation Center, Inc.
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum.


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