From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from mga02.intel.com ([134.134.136.20]:32504 "EHLO mga02.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752843Ab1LUQpf (ORCPT ); Wed, 21 Dec 2011 11:45:35 -0500 Subject: Re: [PATCH 3.2] iwlagn: fix (remove) use of PAGE_SIZE From: "Guy, Wey-Yi" To: "John W. Linville" Cc: "linux-wireless@vger.kernel.org" , "Berg, Johannes" , "Grumbach, Emmanuel" , "stable@vger.kernel.org" In-Reply-To: <20111221161953.GB11842@tuxdriver.com> References: <1324332059-11630-1-git-send-email-wey-yi.w.guy@intel.com> <20111221161953.GB11842@tuxdriver.com> Content-Type: text/plain; charset="UTF-8" Date: Wed, 21 Dec 2011 07:45:00 -0800 Message-ID: <1324482300.13074.295.camel@wwguy-huron> (sfid-20111221_174539_597165_89D7DE09) Mime-Version: 1.0 Sender: linux-wireless-owner@vger.kernel.org List-ID: 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