[PATCH] i2c: smbus: change type of length argument in block functions to size_t

[PATCH] i2c: smbus: change type of length argument in block functions to size_t

[Heiner Kallweit]

Callers may rely on the block functions returning the actually processed
number of bytes, even if the requested number of bytes is larger, e.g.
when used in a loop. However the length argument is of type u8 currently.
This may result in unintended casting and side effects.
If e.g. length == 256, then the effective length would be 0.
Therefore callers that can not guarantee length < 256 have to duplicate
the following check that is done by the block functions already:
if (length > I2C_SMBUS_BLOCK_MAX)
	length = I2C_SMBUS_BLOCK_MAX;
To avoid this change the type of length to size_t.

Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
---
 drivers/i2c/i2c-core-smbus.c | 8 ++++----
 include/linux/i2c.h          | 8 ++++----
 2 files changed, 8 insertions(+), 8 deletions(-)

diff --git a/drivers/i2c/i2c-core-smbus.c b/drivers/i2c/i2c-core-smbus.c
index 304c2c8fe..6fda43317 100644
--- a/drivers/i2c/i2c-core-smbus.c
+++ b/drivers/i2c/i2c-core-smbus.c
@@ -249,7 +249,7 @@ EXPORT_SYMBOL(i2c_smbus_read_block_data);
  * else zero on success.
  */
 s32 i2c_smbus_write_block_data(const struct i2c_client *client, u8 command,
-			       u8 length, const u8 *values)
+			       size_t length, const u8 *values)
 {
 	union i2c_smbus_data data;
 
@@ -265,7 +265,7 @@ EXPORT_SYMBOL(i2c_smbus_write_block_data);
 
 /* Returns the number of read bytes */
 s32 i2c_smbus_read_i2c_block_data(const struct i2c_client *client, u8 command,
-				  u8 length, u8 *values)
+				  size_t length, u8 *values)
 {
 	union i2c_smbus_data data;
 	int status;
@@ -285,7 +285,7 @@ s32 i2c_smbus_read_i2c_block_data(const struct i2c_client *client, u8 command,
 EXPORT_SYMBOL(i2c_smbus_read_i2c_block_data);
 
 s32 i2c_smbus_write_i2c_block_data(const struct i2c_client *client, u8 command,
-				   u8 length, const u8 *values)
+				   size_t length, const u8 *values)
 {
 	union i2c_smbus_data data;
 
@@ -638,7 +638,7 @@ EXPORT_SYMBOL(__i2c_smbus_xfer);
  * transfer.
  */
 s32 i2c_smbus_read_i2c_block_data_or_emulated(const struct i2c_client *client,
-					      u8 command, u8 length, u8 *values)
+					      u8 command, size_t length, u8 *values)
 {
 	u8 i = 0;
 	int status;
diff --git a/include/linux/i2c.h b/include/linux/i2c.h
index 7d4f52ceb..706357241 100644
--- a/include/linux/i2c.h
+++ b/include/linux/i2c.h
@@ -178,14 +178,14 @@ i2c_smbus_write_word_swapped(const struct i2c_client *client,
 s32 i2c_smbus_read_block_data(const struct i2c_client *client,
 			      u8 command, u8 *values);
 s32 i2c_smbus_write_block_data(const struct i2c_client *client,
-			       u8 command, u8 length, const u8 *values);
+			       u8 command, size_t length, const u8 *values);
 /* Returns the number of read bytes */
 s32 i2c_smbus_read_i2c_block_data(const struct i2c_client *client,
-				  u8 command, u8 length, u8 *values);
+				  u8 command, size_t length, u8 *values);
 s32 i2c_smbus_write_i2c_block_data(const struct i2c_client *client,
-				   u8 command, u8 length, const u8 *values);
+				   u8 command, size_t length, const u8 *values);
 s32 i2c_smbus_read_i2c_block_data_or_emulated(const struct i2c_client *client,
-					      u8 command, u8 length,
+					      u8 command, size_t length,
 					      u8 *values);
 int i2c_get_device_id(const struct i2c_client *client,
 		      struct i2c_device_identity *id);
-- 
2.35.1