From: William Lee Irwin III <wli@holomorphy.com>
To: Jeff Garzik <jgarzik@pobox.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>,
James Bottomley <James.Bottomley@steeleye.com>,
Russell King <rmk@arm.linux.org.uk>,
Linux Arch list <linux-arch@vger.kernel.org>,
Linus Torvalds <torvalds@osdl.org>,
David Woodhouse <dwmw2@infradead.org>,
Christoph Hellwig <hch@infradead.org>,
Andrew Morton <akpm@osdl.org>, Andrea Arcangeli <andrea@suse.de>
Subject: Re: can device drivers return non-ram via vm_ops->nopage?
Date: Mon, 22 Mar 2004 14:35:09 -0800 [thread overview]
Message-ID: <20040322223509.GO2045@holomorphy.com> (raw)
In-Reply-To: <405F6636.2090609@pobox.com>
Benjamin Herrenschmidt wrote:
>> You cannot have the mapping coherent in both kernel and user space ? Hrm,
>> I'm afraid drivers won't like that. The DRI will definitely be unhappy,
>> and while I don't think sound drivers need to tap the buffers from the
>> kernel mapping in normal cases, I'm pretty sure things like infiniband
>> or myrinet will have a problem too.
On Mon, Mar 22, 2004 at 05:18:30PM -0500, Jeff Garzik wrote:
> You need both kernel and userspace... for audio drivers, mmap(2) is
> direct to userspace, but read(2) and write(2) must copy_from_user() into
> the allocated DMA area.
This is burned into silicon, so supporting it's not an option. Frankly
I think what's best is another device interface for userspace to fall
back to when this coherent userspace mmap() is unimplementable, e.g.
read()/write() on some device node.
-- wli
next prev parent reply other threads:[~2004-03-22 22:35 UTC|newest]
Thread overview: 105+ messages / expand[flat|nested] mbox.gz Atom feed top
2004-03-20 13:30 can device drivers return non-ram via vm_ops->nopage? Andrea Arcangeli
2004-03-20 14:40 ` William Lee Irwin III
2004-03-20 15:06 ` Andrea Arcangeli
2004-03-20 15:27 ` William Lee Irwin III
2004-03-20 15:44 ` Russell King
2004-03-20 15:57 ` Andrea Arcangeli
2004-03-20 16:15 ` Russell King
2004-03-20 16:25 ` Andrea Arcangeli
2004-03-20 16:57 ` William Lee Irwin III
2004-03-20 17:48 ` Andrea Arcangeli
2004-03-20 19:03 ` Andrea Arcangeli
2004-03-20 15:58 ` Jaroslav Kysela
2004-03-20 16:09 ` Russell King
2004-03-20 19:44 ` Jaroslav Kysela
2004-03-20 22:23 ` Russell King
2004-03-20 22:45 ` William Lee Irwin III
2004-03-20 23:54 ` Russell King
2004-03-21 0:22 ` Zwane Mwaikambo
2004-03-22 4:46 ` Benjamin Herrenschmidt
2004-03-22 18:23 ` Richard Curnow
2004-03-21 0:23 ` William Lee Irwin III
2004-03-21 9:52 ` Arjan van de Ven
2004-03-21 10:39 ` Jaroslav Kysela
2004-03-22 4:43 ` Benjamin Herrenschmidt
2004-03-20 20:13 ` Andrew Morton
2004-03-20 20:28 ` Andrea Arcangeli
2004-03-20 20:50 ` William Lee Irwin III
2004-03-20 22:26 ` Russell King
2004-03-20 22:45 ` William Lee Irwin III
2004-03-21 20:45 ` David Woodhouse
2004-03-21 20:49 ` Christoph Hellwig
2004-03-21 20:57 ` David Woodhouse
2004-03-21 21:53 ` Linus Torvalds
2004-03-21 22:17 ` Jeff Garzik
2004-03-21 22:23 ` David Woodhouse
2004-03-21 22:23 ` Russell King
2004-03-21 22:34 ` Jeff Garzik
2004-03-21 22:42 ` David Woodhouse
2004-03-21 23:06 ` Jeff Garzik
2004-03-21 22:51 ` Russell King
2004-03-21 23:09 ` Jeff Garzik
2004-03-21 23:11 ` Linus Torvalds
2004-03-21 23:22 ` Jeff Garzik
2004-03-21 23:51 ` Linus Torvalds
2004-03-21 23:58 ` Russell King
2004-03-22 0:34 ` Andrea Arcangeli
2004-03-22 3:05 ` Linus Torvalds
2004-03-23 17:59 ` Andy Whitcroft
2004-03-23 17:58 ` David Woodhouse
2004-03-23 18:11 ` William Lee Irwin III
2004-03-22 0:02 ` David Woodhouse
2004-03-22 3:28 ` Linus Torvalds
2004-03-22 0:10 ` Jeff Garzik
2004-03-22 0:20 ` Russell King
2004-03-22 0:33 ` Jeff Garzik
2004-03-22 4:57 ` Benjamin Herrenschmidt
2004-03-21 23:45 ` Russell King
2004-03-22 0:23 ` William Lee Irwin III
2004-03-22 0:29 ` Jeff Garzik
2004-03-22 1:28 ` William Lee Irwin III
2004-03-22 3:45 ` William Lee Irwin III
2004-03-22 4:41 ` James Bottomley
2004-03-22 4:46 ` William Lee Irwin III
2004-03-22 4:56 ` James Bottomley
2004-03-22 5:26 ` Benjamin Herrenschmidt
2004-03-22 11:58 ` Andrea Arcangeli
2004-03-22 12:05 ` Russell King
2004-03-22 12:34 ` Andrea Arcangeli
2004-03-22 9:30 ` Russell King
2004-03-22 15:04 ` James Bottomley
2004-03-22 15:15 ` Russell King
2004-03-22 15:27 ` James Bottomley
2004-03-22 21:50 ` Benjamin Herrenschmidt
2004-03-22 22:18 ` Jeff Garzik
2004-03-22 22:35 ` William Lee Irwin III [this message]
2004-03-22 23:57 ` Benjamin Herrenschmidt
2004-03-23 0:22 ` David Woodhouse
2004-03-23 2:07 ` William Lee Irwin III
2004-03-23 9:28 ` Russell King
2004-03-23 9:34 ` David Woodhouse
2004-03-23 10:04 ` Russell King
2004-03-23 10:05 ` William Lee Irwin III
2004-03-23 11:29 ` Benjamin Herrenschmidt
2004-03-23 11:35 ` Andrea Arcangeli
2004-03-23 11:44 ` William Lee Irwin III
2004-03-23 12:34 ` Andrea Arcangeli
2004-03-23 12:40 ` Russell King
2004-03-23 15:25 ` Linus Torvalds
2004-03-23 15:36 ` Andrea Arcangeli
2004-03-23 15:46 ` Linus Torvalds
2004-03-23 15:50 ` Russell King
2004-03-23 22:10 ` Benjamin Herrenschmidt
2004-03-25 20:25 ` Russell King
2004-03-28 10:17 ` Russell King
2004-03-23 12:49 ` William Lee Irwin III
2004-03-22 23:19 ` Russell King
2004-03-22 23:35 ` Jeff Garzik
2004-03-23 2:26 ` James Bottomley
2004-03-22 6:36 ` William Lee Irwin III
2004-03-20 17:39 ` Linus Torvalds
2004-03-20 17:56 ` Andrea Arcangeli
2004-03-20 18:22 ` William Lee Irwin III
2004-03-21 3:13 ` Chris Wedgwood
2004-03-21 6:23 ` Christoph Hellwig
2004-03-21 7:00 ` Chris Wedgwood
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