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Commit bf263c35 authored by Wolfram Sang's avatar Wolfram Sang Committed by Wolfram Sang
Browse files

i2c: add extra check to safe DMA buffer helper 



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: default avatarHsin-Yi Wang <hsinyi@chromium.org>
Fixes: e94bc5d1 ("i2c: add helpers to ease DMA handling")
Signed-off-by: default avatarWolfram Sang <wsa+renesas@sang-engineering.com>
Reviewed-by: default avatarHsin-Yi Wang <hsinyi@chromium.org>
Signed-off-by: default avatarWolfram Sang <wsa@the-dreams.de>
parent c86da50c

drivers/i2c/i2c-core-base.c

+7 −2
Original line number Diff line number Diff line
@@ -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)