Re: [PATCH] i2c: at91: use dma safe buffers

[Michael Walle <michael@walle.cc>]

Am 2022-04-05 11:23, schrieb Codrin.Ciubotariu@microchip.com:
> On 03.03.2022 18:17, Michael Walle wrote:
>> EXTERNAL EMAIL: Do not click links or open attachments unless you know 
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>> 
>> The supplied buffer might be on the stack and we get the following 
>> error
>> message:
>> [    3.312058] at91_i2c e0070600.i2c: rejecting DMA map of vmalloc 
>> memory
>> 
>> Use i2c_{get,put}_dma_safe_msg_buf() to get a DMA-able memory region 
>> if
>> necessary.
>> 
>> Cc: stable@vger.kernel.org
>> Signed-off-by: Michael Walle <michael@walle.cc>
> 
> Reviewed-by: Codrin Ciubotariu <codrin.ciubotariu@microchip.com>

Thanks!

>> I'm not sure if or which Fixes: tag I should add to this patch. The 
>> issue
>> seems to be since a very long time, but nobody seem to have triggered 
>> it.
>> FWIW, I'm using the sff,sfp driver, which triggers this.
> 
> I think it should be:
> Fixes: 60937b2cdbf9 ("i2c: at91: add dma support")
> 
>> +       if (dev->use_dma) {
>> +               dma_buf = i2c_get_dma_safe_msg_buf(m_start, 1);
> 
> If you want, you could just dev->buf = i2c_get_dma_safe...

But where is the error handling in that case? dev->buf will
be NULL, which is eventually passed to dma_map_single().

Also, I need the dma_buf for the i2c_put_dma_safe_msg_buf()
call anyway, because dev->buf will be modified during
processing.

-michael