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i2c: add extra check to safe DMA buffer helper

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Make sure we report 'no buffer' for 0-length messages. This can only
happen if threshold is set to 0 which is kind of bogus but we should
still handle this situation. Update the docs and add a debug message
to educate callers of this function.

Reported-by: Hsin-Yi Wang <hsinyi@chromium.org>
Fixes: e94bc5d18b ("i2c: add helpers to ease DMA handling")
Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Reviewed-by: Hsin-Yi Wang <hsinyi@chromium.org>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>
This commit is contained in:
Wolfram Sang 2019-03-12 13:44:42 +01:00 committed by Wolfram Sang
parent c86da50cfd
commit bf263c35b2
1 changed files with 7 additions and 2 deletions
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9
drivers/i2c/i2c-core-base.c
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@ -2258,7 +2258,8 @@ EXPORT_SYMBOL(i2c_put_adapter);
/**
* i2c_get_dma_safe_msg_buf() - get a DMA safe buffer for the given i2c_msg
* @msg: the message to be checked
* @threshold: the minimum number of bytes for which using DMA makes sense
* @threshold: the minimum number of bytes for which using DMA makes sense.
* Should at least be 1.
*
* Return: NULL if a DMA safe buffer was not obtained. Use msg->buf with PIO.
* Or a valid pointer to be used with DMA. After use, release it by
@ -2268,7 +2269,11 @@ EXPORT_SYMBOL(i2c_put_adapter);
*/
u8 *i2c_get_dma_safe_msg_buf(struct i2c_msg *msg, unsigned int threshold)
{
if (msg->len < threshold)
/* also skip 0-length msgs for bogus thresholds of 0 */
if (!threshold)
pr_debug("DMA buffer for addr=0x%02x with length 0 is bogus\n",
msg->addr);
if (msg->len < threshold || msg->len == 0)
return NULL;
if (msg->flags & I2C_M_DMA_SAFE)