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Message-Id: <201002171123.30389.oliver@neukum.org>
Date: Wed, 17 Feb 2010 11:23:30 +0100
From: Oliver Neukum <oliver@...kum.org>
To: Benjamin Herrenschmidt <benh@...nel.crashing.org>
Cc: "Shilimkar, Santosh" <santosh.shilimkar@...com>,
Matthew Dharm <mdharm-kernel@...-eyed-alien.net>,
"Russell King - ARM Linux" <linux@....linux.org.uk>,
Ming Lei <tom.leiming@...il.com>,
"Mankad, Maulik Ojas" <x0082077@...com>,
Sergei Shtylyov <sshtylyov@...mvista.com>,
Catalin Marinas <catalin.marinas@....com>,
Sebastian Siewior <bigeasy@...utronix.de>,
"linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
"linux-kernel" <linux-kernel@...r.kernel.org>,
Pavel Machek <pavel@....cz>, Greg KH <greg@...ah.com>,
"linux-arm-kernel" <linux-arm-kernel@...ts.infradead.org>
Subject: Re: USB mass storage and ARM cache coherency
Am Mittwoch, 17. Februar 2010 11:18:01 schrieb Benjamin Herrenschmidt:
> > No problem here. USB core does the mapping only if the low-level driver
> > so requests. The only exception is in usb_buffer_alloc(), but that boils
> > down to dma_alloc_coherent()
>
> Allright, so why do we need to "fix" anything ? Or is the whole thread
> moot ? :-)
The request a low-level driver does is all or nothing. Either DMA
issues have to be handled by that driver alone, or a finer-grained
description of the DMA requirements is needed. A fix using the latter
approach is being worked on.
Regards
Oliver
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