lkml.org 
[lkml]   [2020]   [Nov]   [12]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: [PATCH] iio: ad_sigma_delta: Don't put SPI transfer buffer on the stack
From
Date
On 11/12/20 11:14 AM, Alexandru Ardelean wrote:
> On Thu, Nov 12, 2020 at 11:55 AM Lars-Peter Clausen <lars@metafoo.de> wrote:
>> On 11/12/20 10:10 AM, Alexandru Ardelean wrote:
>>> From: Lars-Peter Clausen <lars@metafoo.de>
>>>
>>> Use a heap allocated memory for the SPI transfer buffer. Using stack memory
>>> can corrupt stack memory when using DMA on some systems.
>>>
>>> This change adds 4 bytes at the end of the current DMA buffer, which will
>>> be used by the trigger handler.
>>> This is required because the first 4 bytes are reserved for register data.
>>>
>>> Fixes: af3008485ea03 ("iio:adc: Add common code for ADI Sigma Delta devices")
>>> Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
>>> Signed-off-by: Alexandru Ardelean <alexandru.ardelean@analog.com>
>>> ---
>>> drivers/iio/adc/ad_sigma_delta.c | 4 ++--
>>> include/linux/iio/adc/ad_sigma_delta.h | 2 +-
>>> 2 files changed, 3 insertions(+), 3 deletions(-)
>>>
>>> diff --git a/drivers/iio/adc/ad_sigma_delta.c b/drivers/iio/adc/ad_sigma_delta.c
>>> index 86039e9ecaca..33297f26508a 100644
>>> --- a/drivers/iio/adc/ad_sigma_delta.c
>>> +++ b/drivers/iio/adc/ad_sigma_delta.c
>>> @@ -395,11 +395,11 @@ static irqreturn_t ad_sd_trigger_handler(int irq, void *p)
>>> struct iio_poll_func *pf = p;
>>> struct iio_dev *indio_dev = pf->indio_dev;
>>> struct ad_sigma_delta *sigma_delta = iio_device_get_drvdata(indio_dev);
>>> + uint8_t *data = &sigma_delta->data[4];
>>> unsigned int reg_size;
>>> unsigned int data_reg;
>>> - uint8_t data[16];
>>>
>>> - memset(data, 0x00, 16);
>>> + memset(data, 0x00, 4);
>> Younger me didn't know what he was doing, this is wrong. We need the
>> extra space for the padding and timestamp.
>>
>> We also can't put the beginning of the buffer at an 4 byte offset since
>> it needs to be 8 byte aligned for the timestamp.
> I'll correct this.
> I was re-spinning this out of some old patches and discussions on this
> that I have.
> So, then this becomes 24 bytes? Or 16?
>
> Something like:
> uint8_t data[24] ____cacheline_aligned;
>
> uint8_t *data = &sigma_delta->data[8];

Yes.

\
 
 \ /
  Last update: 2020-11-12 11:53    [W:0.177 / U:0.116 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site