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[B,5/8] i2c: add a message flag for DMA safe buffers

Message ID 20190425044339.3673-6-kai.heng.feng@canonical.com
State New
Headers show
Series Sync AMD MP2 I2C driver with upstream version | expand

Commit Message

Kai-Heng Feng April 25, 2019, 4:43 a.m. UTC 
BugLink: https://bugs.launchpad.net/bugs/1787775

From: Wolfram Sang <wsa+renesas@sang-engineering.com>

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 <Jonathan.Cameron@huawei.com>
Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>
(cherry picked from commit 521a72e1f2e8141d78e7699eaacda24e308ed428)
Signed-off-by: Kai-Heng Feng <kai.heng.feng@canonical.com>
---
 include/uapi/linux/i2c.h | 3 +++
 1 file changed, 3 insertions(+)
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Patch

diff --git a/include/uapi/linux/i2c.h b/include/uapi/linux/i2c.h
index fe648032d6b9..f71a1751cacf 100644
--- 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 */