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Date: Tue, 03 Nov 2009 08:36:05 +0200 From: Artem Bityutskiy <dedekind1@...il.com> To: Johannes Stezenbach <js@...21.net> Cc: David Woodhouse <dwmw2@...radead.org>, David Brownell <dbrownell@...rs.sourceforge.net>, linux-mtd@...ts.infradead.org, linux-kernel@...r.kernel.org Subject: Re: [PATCH] mtd: m25p80: make command buffer DMA-safe 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 <js@...21.net> > > > 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) -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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