linux-kernel - Re: [PATCH] staging iio: Replace kmalloc with local variable

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Message-ID: <4DEE2D7D.6070506@cam.ac.uk>
Date:	Tue, 07 Jun 2011 14:54:05 +0100
From:	Jonathan Cameron <jic23@....ac.uk>
To:	Ben Dooks <ben-i2c@...ff.org>
CC:	anish <anish198519851985@...il.com>, gregkh@...e.de,
	manuel.stahl@....fraunhofer.de, lucas.demarchi@...fusion.mobi,
	devel@...verdev.osuosl.org, linux-kernel@...r.kernel.org,
	linux-iio@...r.kernel.org, Linux I2C <linux-i2c@...r.kernel.org>
Subject: Re: [PATCH] staging iio: Replace kmalloc with local variable

On 06/07/11 14:41, Ben Dooks wrote:
> 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@...il.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.
Then lets drop this.  Sorry Anish, seems I led you down the garden path.
I'll check all my i2c drivers don't do this...
>  
>>> Signed-off-by: anish kumar <anish198519851985@...il.com>
>> Acked-by: Jonathan Cameron <jic23@....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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> 

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