Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752896Ab1CFPqA (ORCPT ); Sun, 6 Mar 2011 10:46:00 -0500 Received: from ist.d-labs.de ([213.239.218.44]:50384 "EHLO mx01.d-labs.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751930Ab1CFPp6 convert rfc822-to-8bit (ORCPT ); Sun, 6 Mar 2011 10:45:58 -0500 Date: Sun, 6 Mar 2011 16:45:21 +0100 From: Florian Mickler To: Oliver Neukum Cc: mchehab@infradead.org, linux-media@vger.kernel.org, linux-kernel@vger.kernel.org, "Greg Kroah-Hartman" , "Rafael J. Wysocki" , Maciej Rutecki Subject: Re: [PATCH] [media] dib0700: get rid of on-stack dma buffers Message-ID: <20110306164521.2a88a155@schatten.dmk.lab> In-Reply-To: <201103061606.38846.oliver@neukum.org> References: <1299410212-24897-1-git-send-email-florian@mickler.org> <201103061306.10045.oliver@neukum.org> <20110306153805.001011a9@schatten.dmk.lab> <201103061606.38846.oliver@neukum.org> X-Mailer: Claws Mail 3.7.8 (GTK+ 2.20.1; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-15 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1839 Lines: 51 On Sun, 6 Mar 2011 16:06:38 +0100 Oliver Neukum wrote: > Am Sonntag, 6. M?rz 2011, 15:38:05 schrieb Florian Mickler: > > On Sun, 6 Mar 2011 13:06:09 +0100 > > Oliver Neukum wrote: > > > > > Am Sonntag, 6. M?rz 2011, 12:16:52 schrieb Florian Mickler: > > > > > Please take a look at it, as I do not do that much kernel hacking > > > > and don't wanna brake anybodys computer... :) > > > > > > > > From my point of view this should _not_ go to stable even though it would > > > > be applicable. But if someone feels strongly about that and can > > > > take responsibility for that change... > > > > > > The patch looks good and is needed in stable. > > > It could be improved by using a buffer allocated once in the places > > > you hold a mutex anyway. > > > > > > Regards > > > Oliver > > > > Ok, I now put a buffer member in the priv dib0700_state which gets > > allocated on the heap. > > This however is wrong. Just like DMA on the stack this breaks > coherency rules. You may do DMA to the heap in the sense that > you can do DMA to buffers allocated on the heap, but you cannot > do DMA to a part of another structure allocated on the heap. > You need a separate kmalloc for each buffer. > You can reuse the buffer with proper locking, but you must allocate > it seperately once. > > Regards > Oliver Hm.. allocating the buffer in the probe routine and deallocating it in the usb_driver disconnect callback should work? How come that it must be a seperate kmalloc buffer? Is it some aligning that kmalloc garantees? Regards, Flo -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/