linux-kernel - [PATCH v2] soundwire: bus: Make sdw_nwrite() data pointer argument const

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Date:   Wed, 16 Jun 2021 15:59:01 +0100
From:   Richard Fitzgerald <rf@...nsource.cirrus.com>
To:     <vkoul@...nel.org>, <yung-chuan.liao@...ux.intel.com>,
        <pierre-louis.bossart@...ux.intel.com>, <sanyog.r.kale@...el.com>
CC:     <alsa-devel@...a-project.org>, <linux-kernel@...r.kernel.org>,
        <patches@...nsource.cirrus.com>,
        Richard Fitzgerald <rf@...nsource.cirrus.com>
Subject: [PATCH v2] soundwire: bus: Make sdw_nwrite() data pointer argument const

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@...nsource.cirrus.com>
---
 drivers/soundwire/bus.c       | 8 ++++----
 include/linux/soundwire/sdw.h | 2 +-
 2 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/drivers/soundwire/bus.c b/drivers/soundwire/bus.c
index a9e0aa72654d..49c66deba106 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;
 
@@ -535,9 +535,9 @@ EXPORT_SYMBOL(sdw_nread);
  * @slave: SDW Slave
  * @addr: Register address
  * @count: length
- * @val: Buffer for values to be read
+ * @val: Buffer for values to be written
  */
-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 ced07f8fde87..ee45d2984334 100644
--- a/include/linux/soundwire/sdw.h
+++ b/include/linux/soundwire/sdw.h
@@ -1040,7 +1040,7 @@ int sdw_write(struct sdw_slave *slave, u32 addr, u8 value);
 int sdw_write_no_pm(struct sdw_slave *slave, u32 addr, u8 value);
 int sdw_read_no_pm(struct sdw_slave *slave, u32 addr);
 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);
 int sdw_compare_devid(struct sdw_slave *slave, struct sdw_slave_id id);
 void sdw_extract_slave_id(struct sdw_bus *bus, u64 addr, struct sdw_slave_id *id);
 
-- 
2.20.1