i2c: add a message flag for DMA safe buffers

Wolfram Sang · Wolfram Sang · commit 521a72e1f2e8 · 2017-12-03T20:47:33.000+01:00
I2C has no requirement that the buffer of a message needs to be DMA
safe. In case it is, it can now be flagged, so drivers wishing to
do DMA can use the buffer directly.

Reviewed-by: Jonathan Cameron &lt;Jonathan.Cameron@huawei.com&gt;
Signed-off-by: Wolfram Sang &lt;wsa+renesas@sang-engineering.com&gt;
Signed-off-by: Wolfram Sang &lt;wsa@the-dreams.de&gt;
diff --git a/include/uapi/linux/i2c.h b/include/uapi/linux/i2c.h
@@ -72,6 +72,9 @@ struct i2c_msg {
 #define I2C_M_RD		0x0001	/* read data, from slave to master */
 					/* I2C_M_RD is guaranteed to be 0x0001! */
 #define I2C_M_TEN		0x0010	/* this is a ten bit chip address */
+#define I2C_M_DMA_SAFE		0x0200	/* the buffer of this message is DMA safe */
+					/* makes only sense in kernelspace */
+					/* userspace buffers are copied anyway */
 #define I2C_M_RECV_LEN		0x0400	/* length will be first received byte */
 #define I2C_M_NO_RD_ACK		0x0800	/* if I2C_FUNC_PROTOCOL_MANGLING */
 #define I2C_M_IGNORE_NAK	0x1000	/* if I2C_FUNC_PROTOCOL_MANGLING */
