lkml.org 
[lkml]   [2022]   [May]   [5]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH v2] i2c: at91: use dma safe buffers
[+ Wolfram]

Am 2022-05-05 16:51, schrieb Nathan Chancellor:
> On Thu, Apr 07, 2022 at 05:08:28PM +0200, Michael Walle wrote:
>> 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.
>>
>> Fixes: 60937b2cdbf9 ("i2c: at91: add dma support")
>> Signed-off-by: Michael Walle <michael@walle.cc>
>> Reviewed-by: Codrin Ciubotariu <codrin.ciubotariu@microchip.com>
>> ---
>> changes since v1:
>> - remove extra empty line
>> - add fixes tag as suggested by Codrin
>>
>> drivers/i2c/busses/i2c-at91-master.c | 11 +++++++++++
>> 1 file changed, 11 insertions(+)
>>
>> diff --git a/drivers/i2c/busses/i2c-at91-master.c
>> b/drivers/i2c/busses/i2c-at91-master.c
>> index b0eae94909f4..5eca3b3bb609 100644
>> --- a/drivers/i2c/busses/i2c-at91-master.c
>> +++ b/drivers/i2c/busses/i2c-at91-master.c
>> @@ -656,6 +656,7 @@ static int at91_twi_xfer(struct i2c_adapter *adap,
>> struct i2c_msg *msg, int num)
>> unsigned int_addr_flag = 0;
>> struct i2c_msg *m_start = msg;
>> bool is_read;
>> + u8 *dma_buf;
>>
>> dev_dbg(&adap->dev, "at91_xfer: processing %d messages:\n", num);
>>
>> @@ -703,7 +704,17 @@ static int at91_twi_xfer(struct i2c_adapter
>> *adap, struct i2c_msg *msg, int num)
>> dev->msg = m_start;
>> dev->recv_len_abort = false;
>>
>> + if (dev->use_dma) {
>> + dma_buf = i2c_get_dma_safe_msg_buf(m_start, 1);
>> + if (!dma_buf) {
>> + ret = -ENOMEM;
>> + goto out;
>> + }
>> + dev->buf = dma_buf;
>> + }
>> +
>> ret = at91_do_twi_transfer(dev);
>> + i2c_put_dma_safe_msg_buf(dma_buf, m_start, !ret);
>>
>> ret = (ret < 0) ? ret : num;
>> out:
>> --
>> 2.30.2
>>
>>
>
> This change as commit 03fbb903c8bf ("i2c: at91: use dma safe buffers")
> causes the following clang warning:

Ugh..

> drivers/i2c/busses/i2c-at91-master.c:707:6: error: variable 'dma_buf'
> is used uninitialized whenever 'if' condition is false
> [-Werror,-Wsometimes-uninitialized]
> if (dev->use_dma) {
> ^~~~~~~~~~~~
> drivers/i2c/busses/i2c-at91-master.c:717:27: note: uninitialized use
> occurs here
> i2c_put_dma_safe_msg_buf(dma_buf, m_start, !ret);
> ^~~~~~~
> drivers/i2c/busses/i2c-at91-master.c:707:2: note: remove the 'if' if
> its condition is always true
> if (dev->use_dma) {
> ^~~~~~~~~~~~~~~~~~
> drivers/i2c/busses/i2c-at91-master.c:659:13: note: initialize the
> variable 'dma_buf' to silence this warning
> u8 *dma_buf;
> ^
> = NULL
> 1 error generated.
>
> Should this variable be initialized or should the call to
> i2c_put_dma_safe_msg_buf() be moved into the if statement?

Initializing dma_buf with NULL should to the trick because
i2c_put_dma_safe_msg_buf() is handling NULL gracefully. No
need for an extra "if (dma_buf)".

Will you take care or should I send a patch?

-michael

\
 
 \ /
  Last update: 2022-05-05 17:13    [W:0.109 / U:1.228 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site