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

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Message-ID: <544AC56F16B56944AEC3BD4E3D5917713AAF3C9C0F@LIMKCMBX1.ad.analog.com>
Date:	Tue, 7 Jun 2011 15:04:32 +0100
From:	"Hennerich, Michael" <Michael.Hennerich@...log.com>
To:	Jonathan Cameron <jic23@....ac.uk>, Ben Dooks <ben-i2c@...ff.org>
CC:	anish <anish198519851985@...il.com>,
	"gregkh@...e.de" <gregkh@...e.de>,
	"manuel.stahl@....fraunhofer.de" <manuel.stahl@....fraunhofer.de>,
	"lucas.demarchi@...fusion.mobi" <lucas.demarchi@...fusion.mobi>,
	"devel@...verdev.osuosl.org" <devel@...verdev.osuosl.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-iio@...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

Jonathan Cameron wrote on 2011-06-07:
> 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...

Can you point to a i2c bus driver that does dma and uses the buffer from the
client directly?

>>
>>>> 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;
>>>>  }
>>>
>>> --
>>> To unsubscribe from this list: send the line "unsubscribe linux-i2c"
>>> in the body of a message to majordomo@...r.kernel.org More
>>> majordomo info at  http://vger.kernel.org/majordomo-info.html
>>
>

Greetings,
Michael

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