From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from charlotte.tuxdriver.com ([70.61.120.58]:55299 "EHLO smtp.tuxdriver.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752250Ab1LUQaf (ORCPT ); Wed, 21 Dec 2011 11:30:35 -0500 Date: Wed, 21 Dec 2011 11:19:54 -0500 From: "John W. Linville" To: Wey-Yi Guy Cc: linux-wireless@vger.kernel.org, Johannes Berg , Emmanuel Grumbach , stable@vger.kernel.org Subject: Re: [PATCH 3.2] iwlagn: fix (remove) use of PAGE_SIZE Message-ID: <20111221161953.GB11842@tuxdriver.com> (sfid-20111221_173045_728203_3F177509) References: <1324332059-11630-1-git-send-email-wey-yi.w.guy@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: <1324332059-11630-1-git-send-email-wey-yi.w.guy@intel.com> Sender: linux-wireless-owner@vger.kernel.org List-ID: 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? John -- John W. Linville Someday the world will need a hero, and you linville@tuxdriver.com might be all we have. Be ready.