[PATCH] soundwire: bus: Make sdw_nwrite() data pointer argument const

[Richard Fitzgerald <rf@opensource.cirrus.com>]

Idiomatically, write functions should take const pointers to the
data buffer, as they don't change the data. They are also likely to
be called from functions that receive a const data pointer.

Internally the pointer is passed to function/structs shared with
the read functions, requiring a cast, but this is an implementation
detail that should be hidden by the public API.

Signed-off-by: Richard Fitzgerald <rf@opensource.cirrus.com>
---
 drivers/soundwire/bus.c       | 6 +++---
 include/linux/soundwire/sdw.h | 2 +-
 2 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/drivers/soundwire/bus.c b/drivers/soundwire/bus.c
index d9deafdcf495..4c76358416c5 100644
--- a/drivers/soundwire/bus.c
+++ b/drivers/soundwire/bus.c
@@ -394,13 +394,13 @@ sdw_nread_no_pm(struct sdw_slave *slave, u32 addr, size_t count, u8 *val)
 }
 
 static int
-sdw_nwrite_no_pm(struct sdw_slave *slave, u32 addr, size_t count, u8 *val)
+sdw_nwrite_no_pm(struct sdw_slave *slave, u32 addr, size_t count, const u8 *val)
 {
 	struct sdw_msg msg;
 	int ret;
 
 	ret = sdw_fill_msg(&msg, slave, addr, count,
-			   slave->dev_num, SDW_MSG_FLAG_WRITE, val);
+			   slave->dev_num, SDW_MSG_FLAG_WRITE, (u8 *)val);
 	if (ret < 0)
 		return ret;
 
@@ -524,7 +524,7 @@ EXPORT_SYMBOL(sdw_nread);
  * @count: length
  * @val: Buffer for values to be read
  */
-int sdw_nwrite(struct sdw_slave *slave, u32 addr, size_t count, u8 *val)
+int sdw_nwrite(struct sdw_slave *slave, u32 addr, size_t count, const u8 *val)
 {
 	int ret;
 
diff --git a/include/linux/soundwire/sdw.h b/include/linux/soundwire/sdw.h
index f0b01b728640..18f5979d9a60 100644
--- a/include/linux/soundwire/sdw.h
+++ b/include/linux/soundwire/sdw.h
@@ -1006,6 +1006,6 @@ int sdw_bus_exit_clk_stop(struct sdw_bus *bus);
 int sdw_read(struct sdw_slave *slave, u32 addr);
 int sdw_write(struct sdw_slave *slave, u32 addr, u8 value);
 int sdw_nread(struct sdw_slave *slave, u32 addr, size_t count, u8 *val);
-int sdw_nwrite(struct sdw_slave *slave, u32 addr, size_t count, u8 *val);
+int sdw_nwrite(struct sdw_slave *slave, u32 addr, size_t count, const u8 *val);
 
 #endif /* __SOUNDWIRE_H */
-- 
2.20.1