From: Jeff Garzik <jgarzik@pobox.com>
To: Russell King <rmk+lkml@arm.linux.org.uk>
Cc: Linus Torvalds <torvalds@osdl.org>,
David Woodhouse <dwmw2@infradead.org>,
Christoph Hellwig <hch@infradead.org>,
William Lee Irwin III <wli@holomorphy.com>,
Andrew Morton <akpm@osdl.org>, Andrea Arcangeli <andrea@suse.de>,
linux-kernel@vger.kernel.org
Subject: Re: can device drivers return non-ram via vm_ops->nopage?
Date: Sun, 21 Mar 2004 19:33:42 -0500 [thread overview]
Message-ID: <405E3466.8070401@pobox.com> (raw)
In-Reply-To: <20040322002041.I26708@flint.arm.linux.org.uk>
Russell King wrote:
> On Sun, Mar 21, 2004 at 07:10:53PM -0500, Jeff Garzik wrote:
>
>>For the first kind, please read fb_mmap in drivers/video/fbmem.c. Look
>>at the _horror_ of ifdefs in exporting the framebuffer. And that horror
>>is what's often needed when letting userspace mmap(2) PCI memory IO regions.
>
>
> Most of this:
[...]
> exists because architectures haven't defined their private
> pgprot_writecombine() implementations, preferring instead to add
> to the preprocessor junk instead.
Agreed but the larger point is that that code should not be in fbmem.c
at all.
There are two main types of usage for bus IO memory (MMIO), data and
hardware registers. Both types driver writers currently export to
userspace via mmap(2). Caching and write combining are simply
driver-controlled attributes one must consider.
Jeff
next prev parent reply other threads:[~2004-03-22 0:34 UTC|newest]
Thread overview: 67+ 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 [this message]
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 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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