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From:   Richard Fitzgerald <rf@opensource.cirrus.com>
To:     <vkoul@kernel.org>, <yung-chuan.liao@linux.intel.com>,
        <pierre-louis.bossart@linux.intel.com>, <sanyog.r.kale@intel.com>
CC:     <alsa-devel@alsa-project.org>, <linux-kernel@vger.kernel.org>,
        <patches@opensource.cirrus.com>,
        Richard Fitzgerald <rf@opensource.cirrus.com>
Subject: [PATCH v2] soundwire: bus: Make sdw_nwrite() data pointer argument const
Date:   Wed, 16 Jun 2021 15:59:01 +0100
Message-ID: <20210616145901.29402-1-rf@opensource.cirrus.com>
MIME-Version: 1.0
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Precedence: bulk

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       | 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