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@xxxxxxxx>
> Reviewed-by: Codrin Ciubotariu <codrin.ciubotariu@xxxxxxxxxxxxx>
> ---
> 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:
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?
Cheers,
Nathan
