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Date: Tue, 7 Jun 2011 14:41:35 +0100
From: Ben Dooks <ben-i2c@fluff.org>
To: Jonathan Cameron <jic23@cam.ac.uk>
Cc: anish <anish198519851985@gmail.com>, gregkh@suse.de,
        manuel.stahl@iis.fraunhofer.de, lucas.demarchi@profusion.mobi,
        devel@driverdev.osuosl.org, linux-kernel@vger.kernel.org,
        linux-iio@vger.kernel.org, Linux I2C <linux-i2c@vger.kernel.org>
Subject: Re: [PATCH] staging iio: Replace kmalloc with local variable
Message-ID: <20110607134135.GD15795@trinity.fluff.org>
References: <1307450354.1516.23.camel@anish-desktop> <4DEE20E7.4020008@cam.ac.uk>
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On Tue, Jun 07, 2011 at 02:00:23PM +0100, Jonathan Cameron wrote:
> On 06/07/11 13:39, anish wrote:
> > From: anish kumar <anish198519851985@gmail.com>
> > 
> > replaced kmalloc with local variable as I2C(in this case) doesn't require
> > kmalloc memory it can do with stack memory.
> I've cc'd linux-i2c just to check I'm right about the whole i2c doesn't need
> dma safe buffers bit...

No, it is down to the i2c driver, and from recollection dma from stack is
not recommended, due to things like cache line alignment. Please do not
do this.
 
> > Signed-off-by: anish kumar <anish198519851985@gmail.com>
> Acked-by: Jonathan Cameron <jic23@cam.ac.uk>
> > ---
> >  drivers/staging/iio/adc/max1363_core.c |    5 +----
> >  1 files changed, 1 insertions(+), 4 deletions(-)
> > 
> > diff --git a/drivers/staging/iio/adc/max1363_core.c b/drivers/staging/iio/adc/max1363_core.c
> > index 1037087..9462230 100644
> > --- a/drivers/staging/iio/adc/max1363_core.c
> > +++ b/drivers/staging/iio/adc/max1363_core.c
> > @@ -207,15 +207,12 @@ static int max1363_write_basic_config(struct i2c_client *client,
> >  				      unsigned char d2)
> >  {
> >  	int ret;
> > -	u8 *tx_buf = kmalloc(2, GFP_KERNEL);
> > +	u8 tx_buf[2];
> >  
> > -	if (!tx_buf)
> > -		return -ENOMEM;
> >  	tx_buf[0] = d1;
> >  	tx_buf[1] = d2;
> >  
> >  	ret = i2c_master_send(client, tx_buf, 2);
> > -	kfree(tx_buf);
> >  
> >  	return (ret > 0) ? 0 : ret;
> >  }
> 
> --
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-- 
Ben Dooks, ben@fluff.org, http://www.fluff.org/ben/

Large Hadron Colada: A large Pina Colada that makes the universe disappear.

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