From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from mail-bw0-f46.google.com ([209.85.214.46]:55661 "EHLO mail-bw0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752771Ab1DSGI3 (ORCPT ); Tue, 19 Apr 2011 02:08:29 -0400 Received: by bwz15 with SMTP id 15so4269180bwz.19 for ; Mon, 18 Apr 2011 23:08:28 -0700 (PDT) Message-ID: <4DAD26D9.6060906@suse.cz> Date: Tue, 19 Apr 2011 08:08:25 +0200 From: Jiri Slaby MIME-Version: 1.0 To: Linus Torvalds CC: Russell King - ARM Linux , Janusz Krzysztofik , Linux Media Mailing List , linux-arm-kernel@lists.infradead.org, Mauro Carvalho Chehab , Jiri Slaby Subject: [REVERT] Re: V4L: videobuf-dma-contig: fix mmap_mapper broken on ARM References: <201104122306.34909.jkrzyszt@tis.icnet.pl> <201104131252.32011.jkrzyszt@tis.icnet.pl> <20110413183231.GA23631@n2100.arm.linux.org.uk> <201104132256.40325.jkrzyszt@tis.icnet.pl> <20110413220008.GA23901@n2100.arm.linux.org.uk> In-Reply-To: <20110413220008.GA23901@n2100.arm.linux.org.uk> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit List-ID: Sender: On 04/14/2011 12:00 AM, Russell King - ARM Linux wrote: > On Wed, Apr 13, 2011 at 10:56:39PM +0200, Janusz Krzysztofik wrote: >> Dnia środa 13 kwiecień 2011 o 20:32:31 Russell King - ARM Linux >> napisał(a): >>> On Wed, Apr 13, 2011 at 12:52:31PM +0200, Janusz Krzysztofik wrote: >>>> Taking into account that I'm just trying to fix a regression, and >>>> not invent a new, long term solution: are you able to name an ARM >>>> based board which a) is already supported in 2.6.39, b) is (or can >>>> be) equipped with a device supported by a V4L driver which uses >>>> videobuf- dma-config susbsystem, c) has a bus structure with which >>>> virt_to_phys(bus_to_virt(dma_handle)) is not equal dma_handle? >>> >>> I have no idea - and why should whether someone can name something >>> that may break be a justification to allow something which is >>> technically wrong? >>> >>> Surely it should be the other way around - if its technically wrong >>> and _may_ break something then it shouldn't be allowed. >> >> In theory - of course. In practice - couldn't we now, close to -rc3, >> relax the rules a little bit and stop bothering with something that may >> break in the future if it doesn't break on any board supported so far (I >> hope)? > > If we are worried about closeness to -final, then what should happen is > that the original commit is reverted; the "fix" for IOMMUs resulted in > a regression for existing users which isn't trivial to resolve without > risking possible breakage of other users. Hi, as -rc4 is out, I think it's time to revert that commit and rethink the mmap behaviour for some of next -rc1s. Linus, please revert commit 35d9f510b67b10338161aba6229d4f55b4000f5b Author: Jiri Slaby Date: Mon Feb 28 06:37:02 2011 -0300 [media] V4L: videobuf, don't use dma addr as physical === It fixes mmap when IOMMU is used on x86 only, but breaks architectures like ARM or PPC where virt_to_phys(dma_alloc_coherent) doesn't work. We need there dma_mmap_coherent or similar (the trickery what snd_pcm_default_mmap does but in some saner way). But this cannot be done at this phase. thanks, -- js suse labs