i2c: Functions for byte-swapped smbus_write/read_word_data

Reimplemented at least 17 times discounting error mangling cases
where it could be used.

Signed-off-by: Jonathan Cameron <jic23@cam.ac.uk>
Signed-off-by: Jean Delvare <khali@linux-fr.org>

2 files changed, 25 insertions, 0 deletions

diff --git a/Documentation/i2c/smbus-protocol b/Documentation/i2c/smbus-protocol
index 7c19d1a2bea0..49f5b680809d 100644
--- a/Documentation/i2c/smbus-protocol
+++ b/Documentation/i2c/smbus-protocol
@@ -88,6 +88,10 @@ byte. But this time, the data is a complete word (16 bits).
 
 S Addr Wr [A] Comm [A] S Addr Rd [A] [DataLow] A [DataHigh] NA P
 
+Note the convenience function i2c_smbus_read_word_swapped is
+available for reads where the two data bytes are the other way
+around (not SMBus compliant, but very popular.)
+
 
 SMBus Write Byte:  i2c_smbus_write_byte_data()
 ==============================================
@@ -108,6 +112,10 @@ specified through the Comm byte.
 
 S Addr Wr [A] Comm [A] DataLow [A] DataHigh [A] P
 
+Note the convenience function i2c_smbus_write_word_swapped is
+available for writes where the two data bytes are the other way
+around (not SMBus compliant, but very popular.)
+
 
 SMBus Process Call:  i2c_smbus_process_call()
 =============================================
diff --git a/include/linux/i2c.h b/include/linux/i2c.h
index a6c652ef516d..38a21c3edd2c 100644
--- a/include/linux/i2c.h
+++ b/include/linux/i2c.h
@@ -34,6 +34,7 @@
 #include <linux/sched.h>        /* for completion */
 #include <linux/mutex.h>
 #include <linux/of.h>           /* for struct device_node */
+#include <linux/swab.h>         /* for swab16 */
 
 extern struct bus_type i2c_bus_type;
 extern struct device_type i2c_adapter_type;
@@ -88,6 +89,22 @@ extern s32 i2c_smbus_read_word_data(const struct i2c_client *client,
                                     u8 command);
 extern s32 i2c_smbus_write_word_data(const struct i2c_client *client,
                                      u8 command, u16 value);
+
+static inline s32
+i2c_smbus_read_word_swapped(const struct i2c_client *client, u8 command)
+{
+        s32 value = i2c_smbus_read_word_data(client, command);
+
+        return (value < 0) ? value : swab16(value);
+}
+
+static inline s32
+i2c_smbus_write_word_swapped(const struct i2c_client *client,
+                             u8 command, u16 value)
+{
+        return i2c_smbus_write_word_data(client, command, swab16(value));
+}
+
 /* Returns the number of read bytes */
 extern s32 i2c_smbus_read_block_data(const struct i2c_client *client,
                                      u8 command, u8 *values);