From: Jeff Garzik <jgarzik@pobox.com>
To: Russell King <rmk@arm.linux.org.uk>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>,
James Bottomley <James.Bottomley@steeleye.com>,
William Lee Irwin III <wli@holomorphy.com>,
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 18:35:19 -0500 [thread overview]
Message-ID: <405F7837.2010800@pobox.com> (raw)
In-Reply-To: <20040322231933.H11212@flint.arm.linux.org.uk>
Russell King wrote:
> 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.
>
>
> Not actually true in this case - audio drivers are either mmap() only
> or read/write only, never both at the same time.
Agreed, but due to OSS dain bramage you can read/write as much as you
like, up until the mmap point, AFAICS. It's much easier for the driver
to allocate one set of buffers, than to allocate a set at open(2), throw
away those allocs at mmap(2) and make new ones.
Jeff
next prev parent reply other threads:[~2004-03-22 23:35 UTC|newest]
Thread overview: 38+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20040321204931.A11519@infradead.org>
[not found] ` <1079902670.17681.324.camel@imladris.demon.co.uk>
[not found] ` <Pine.LNX.4.58.0403211349340.1106@ppc970.osdl.org>
[not found] ` <20040321222327.D26708@flint.arm.linux.org.uk>
[not found] ` <405E1859.5030906@pobox.com>
[not found] ` <20040321225117.F26708@flint.arm.linux.org.uk>
[not found] ` <Pine.LNX.4.58.0403211504550.1106@ppc970.osdl.org>
[not found] ` <20040321234515.G26708@flint.arm.linux.org.uk>
[not found] ` <20040322002349.GZ2045@holomorphy.com>
[not found] ` <405E3387.1050505@pobox.com>
2004-03-22 3:45 ` can device drivers return non-ram via vm_ops->nopage? 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
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 [this message]
2004-03-23 2:26 ` James Bottomley
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