From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754181AbbCSJy6 (ORCPT ); Thu, 19 Mar 2015 05:54:58 -0400 Received: from cantor2.suse.de ([195.135.220.15]:51333 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751195AbbCSJy5 (ORCPT ); Thu, 19 Mar 2015 05:54:57 -0400 Message-ID: <1426758862.2814.4.camel@suse.de> Subject: Re: [PATCH] HID: sony: Enable Gasia third-party PS3 controllers From: Oliver Neukum To: Pavel Machek Cc: Jiri Kosina , Lauri Kasanen , linux-input@vger.kernel.org, linux-kernel@vger.kernel.org, ao2@ao2.it, AndrewD207@aol.com Date: Thu, 19 Mar 2015 10:54:22 +0100 In-Reply-To: <20150319093834.GB18997@amd> References: <20150207154859.89a7e4e3.cand@gmx.com> <1423476481.10695.2.camel@linux-0dmf.site> <20150209204414.a4d205be.cand@gmx.com> <1423556076.19839.3.camel@linux-0dmf.site> <20150316211056.GB11441@amd> <1426756461.3815.3.camel@suse.de> <20150319093834.GB18997@amd> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.12.9 Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 2015-03-19 at 10:38 +0100, Pavel Machek wrote: > On Thu 2015-03-19 10:14:21, Oliver Neukum wrote: > > On Mon, 2015-03-16 at 22:37 +0100, Jiri Kosina wrote: > > > Are you sure CONFIG_DMA_API_DEBUG wouldn't warn here? > > > > As far as I can tell, it will not warn. The problem is not in the > > mapping itself. That is usually legitimate. The problem arises > > because the buffer doesn't have a cacheline of its own. Thus the > > memory corruption happens after the IO operation has started. > > Nasty. Would WARN_ON(buffer & CACHELINE_SIZE-1) do at least part of No. It is perfectly legitimate to put your buffer at an offset or to combine buffers provided you don't use them at the same time. > the trick? Alternatively, could we call ksize() on the object, and > fail if it is not big enough? What object? We have a pointer to a memory location. > Alternatively, we could create "allocate_for_usb" function, and only > take pointers allocated by that function in usb functions. That would > also teach people the problem exists... No, this problem is not limited to USB. Regards Oliver