Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754863Ab1CXLKJ (ORCPT ); Thu, 24 Mar 2011 07:10:09 -0400 Received: from mail-ww0-f44.google.com ([74.125.82.44]:62340 "EHLO mail-ww0-f44.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751458Ab1CXLKE (ORCPT ); Thu, 24 Mar 2011 07:10:04 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=subject:from:reply-to:to:cc:in-reply-to:references:content-type :date:message-id:mime-version:x-mailer:content-transfer-encoding; b=AlawyT1oACANe78PKZHWhVXeE1mJlIqgZg7iXyyM3fGQwgiYc7Q7Tw9s+JP29HiA/t pEi8WpIuy5bSOXJTd8GMBfHYFnWTVjaYaqfWOnYaOJ3jRxjq91u2OGKkZ/Z7IkiAPShY L/GJpiuc/462dtRYq9InG0F3RK1S5Wg1cVTv0= Subject: Re: Hit BUG_ON in dma-mapping.c:425 (RFC) From: Artem Bityutskiy Reply-To: dedekind1@gmail.com To: Russell King - ARM Linux Cc: Nicolas Ferre , "'linux-arm-kernel@lists.infradead.org'" , Linux Kernel list , Patrice VILCHEZ , Hong XU , Jean-Christophe PLAGNIOL-VILLARD , Andrew Victor , linux-mtd In-Reply-To: <20110324092732.GA19935@n2100.arm.linux.org.uk> References: <4D24A108.2080609@atmel.com> <4D8AFE45.8050609@atmel.com> <20110324082521.GB9844@n2100.arm.linux.org.uk> <1300955778.2735.68.camel@localhost> <20110324092732.GA19935@n2100.arm.linux.org.uk> Content-Type: text/plain; charset="UTF-8" Date: Thu, 24 Mar 2011 13:08:07 +0200 Message-ID: <1300964887.2735.84.camel@localhost> Mime-Version: 1.0 X-Mailer: Evolution 2.32.1 (2.32.1-1.fc14) Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1168 Lines: 27 On Thu, 2011-03-24 at 09:27 +0000, Russell King - ARM Linux wrote: > The only real answer I can give is: if you want to deal with DMA, you > absolutely must conform to the restrictions on DMA which means that you > can't pass vmalloc addresses to the DMA API. I see, thanks. Well, I do not see any issues with changing MTD-related SW (JFFS2, UBI, UBIFS, etc) to use kmalloc. But this would require som non-trivial efforts, although I believe this is doable. Basically, we have to work with entire eraseblocks often, which may be 128KiB or 256KiB or even 512KiB nowadays. And we vmalloc the eraseblock-sized buffers in these cases. We could instead work with arrays of pages (or multiple pages), and then do things like readv/writev. But this requires a brave knight who'd come and just implemented this, or a company who'd fund someone to work on this. -- Best Regards, Artem Bityutskiy (Артём Битюцкий) -- 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/