From mboxrd@z Thu Jan 1 00:00:00 1970 Subject: Re: Hit BUG_ON in dma-mapping.c:425 (RFC) From: Artem Bityutskiy To: Russell King - ARM Linux 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 Content-Transfer-Encoding: 8bit Cc: Hong XU , Nicolas Ferre , Patrice VILCHEZ , Linux Kernel list , linux-mtd , Jean-Christophe PLAGNIOL-VILLARD , Andrew Victor , "'linux-arm-kernel@lists.infradead.org'" Reply-To: dedekind1@gmail.com List-Id: Linux MTD discussion mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , 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)