From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from charlotte.tuxdriver.com ([70.61.120.58]:40243 "EHLO smtp.tuxdriver.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752900Ab1LUUAg (ORCPT ); Wed, 21 Dec 2011 15:00:36 -0500 Date: Wed, 21 Dec 2011 14:58:21 -0500 From: "John W. Linville" To: "Guy, Wey-Yi" Cc: "linux-wireless@vger.kernel.org" , "Berg, Johannes" , "Grumbach, Emmanuel" , "stable@vger.kernel.org" Subject: Re: [PATCH 3.2] iwlagn: fix (remove) use of PAGE_SIZE Message-ID: <20111221195821.GF11842@tuxdriver.com> (sfid-20111221_210040_335225_9F381B36) References: <1324332059-11630-1-git-send-email-wey-yi.w.guy@intel.com> <20111221161953.GB11842@tuxdriver.com> <1324482300.13074.295.camel@wwguy-huron> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: <1324482300.13074.295.camel@wwguy-huron> Sender: linux-wireless-owner@vger.kernel.org List-ID: On Wed, Dec 21, 2011 at 07:45:00AM -0800, Guy, Wey-Yi wrote: > Hi John, > > On Wed, 2011-12-21 at 08:19 -0800, John W. Linville wrote: > > On Mon, Dec 19, 2011 at 02:00:59PM -0800, Wey-Yi Guy wrote: > > > From: Johannes Berg > > > > > > The ICT code erroneously uses PAGE_SIZE. The bug > > > is that PAGE_SIZE isn't necessarily 4096, so on > > > such platforms this code will not work correctly > > > as we'll try to attempt to read an index in the > > > table that the device never wrote, it always has > > > 4096-byte pages. > > > > > > Additionally, the manual alignment code here is > > > unnecessary -- Documentation/DMA-API-HOWTO.txt > > > states: > > > The cpu return address and the DMA bus master address are both > > > guaranteed to be aligned to the smallest PAGE_SIZE order which > > > is greater than or equal to the requested size. This invariant > > > exists (for example) to guarantee that if you allocate a chunk > > > which is smaller than or equal to 64 kilobytes, the extent of the > > > buffer you receive will not cross a 64K boundary. > > > > > > Just use appropriate new constants and get rid of > > > the alignment code. > > > > > > Cc: Emmanuel Grumbach > > > Cc: stable@vger.kernel.org > > > Signed-off-by: Johannes Berg > > > Signed-off-by: Wey-Yi Guy > > > > This seems like a big patch. It is a bit late in the release cycle > > to rewrite all the DMA allocation code. :-) > > > > What platforms does this affect? Are there actual users involved? > > I understand the patch is bigger than the regular patch should be > generated for stable kernel. Johannes can explain better, but he is on > vacation. as what I understood, he work with community user who > encounter issue and root cause it is PAGE SIZE cause the problem. > > Thanks > Wey Unless someone screams, I'd be a lot more comfortable saving this for 3.3. John -- John W. Linville Someday the world will need a hero, and you linville@tuxdriver.com might be all we have. Be ready.