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From: "David S. Miller" <davem@redhat.com>
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Date: Mon, 5 Mar 2001 20:53:21 -0800 (PST)
To: Russell King <rmk@arm.linux.org.uk>
Cc: David Brownell <david-b@pacbell.net>,
        Manfred Spraul <manfred@colorfullife.com>, zaitcev@redhat.com,
        linux-usb-devel@lists.sourceforge.net, linux-kernel@vger.kernel.org
Subject: Re: SLAB vs. pci_alloc_xxx in usb-uhci patch
In-Reply-To: <20010305232053.A16634@flint.arm.linux.org.uk>
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Russell King writes:
 > A while ago, I looked at what was required to convert the OHCI driver
 > to pci_alloc_consistent, and it turns out that the current interface is
 > highly sub-optimal.  It looks good on the face of it, but it _really_
 > does need sub-page allocations to make sense for USB.
 > 
 > At the time, I didn't feel like creating a custom sub-allocator just
 > for USB, and since then I haven't had the inclination nor motivation
 > to go back to trying to get my USB mouse or iPAQ communicating via USB.
 > (I've not used this USB port for 3 years anyway).

Gerard Roudier wrote for the sym53c8xx driver the exact thing
UHCI/OHCI need for this.

I think people are pissing their pants over the pci_alloc_consistent
interface for no reason.  It gives PAGE<<order sized/aligned chunks
back to the caller at the request of Linus so that drivers did not
have to guess "is this 16-byte aligned..." etc.

Later,
David S. Miller
davem@redhat.com
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