From mboxrd@z Thu Jan 1 00:00:00 1970 Subject: Re: [PATCH] mtd: m25p80: make command buffer DMA-safe From: Artem Bityutskiy To: Johannes Stezenbach In-Reply-To: <20091028132137.GA17813@sig21.net> References: <20091028132137.GA17813@sig21.net> Content-Type: text/plain; charset="UTF-8" Date: Tue, 03 Nov 2009 08:36:05 +0200 Message-Id: <1257230165.21596.33.camel@localhost> Mime-Version: 1.0 Content-Transfer-Encoding: 8bit Cc: linux-mtd@lists.infradead.org, David Brownell , David Woodhouse , linux-kernel@vger.kernel.org Reply-To: dedekind1@gmail.com List-Id: Linux MTD discussion mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Wed, 2009-10-28 at 14:21 +0100, Johannes Stezenbach wrote: > spi_write() requires the buffer to be DMA-safe, kmalloc() > it seperately to ensure this. > > Signed-off-by: Johannes Stezenbach > > > diff --git a/drivers/mtd/devices/m25p80.c b/drivers/mtd/devices/m25p80.c > index 4c19269..21dd4d9 100644 > --- a/drivers/mtd/devices/m25p80.c > +++ b/drivers/mtd/devices/m25p80.c > @@ -79,7 +79,7 @@ struct m25p { > struct mtd_info mtd; > unsigned partitioned:1; > u8 erase_opcode; > - u8 command[CMD_SIZE + FAST_READ_DUMMY_BYTE]; > + u8 *command; > }; > > static inline struct m25p *mtd_to_m25p(struct mtd_info *mtd) > @@ -770,6 +770,11 @@ static int __devinit m25p_probe(struct spi_device *spi) > flash = kzalloc(sizeof *flash, GFP_KERNEL); > if (!flash) > return -ENOMEM; > + flash->command = kmalloc(CMD_SIZE + FAST_READ_DUMMY_BYTE, GFP_KERNEL); > + if (!flash->command) { > + kfree(flash); > + return -ENOMEM; > + } Even though it is just 4 or 5 bytes it can do DMA? Does not sound too sane to use DMA in that case. Does this patch fix a real error? I do not know much about SPI, but for me it sounds like there should be a method to ask SPI to avoid using DMA, and you should use that method. -- Best Regards, Artem Bityutskiy (Артём Битюцкий)