[PATCH] i2c: boilerplate function for byte swapped smbus_write/read_word_data

[Jonathan Cameron <jic23-KWPb1pKIrIJaa/9Udqfwiw@public.gmane.org>]

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

Signed-off-by: Jonathan Cameron <jic23-KWPb1pKIrIJaa/9Udqfwiw@public.gmane.org>
---

Hi All,

Quite a number of devices rather unhelpfully handle smbus read/write word
commands but return the result byte swapped.  Hence drivers swap it back
again.

Examples based on quick grep or read users that byte swap(write is completely trivial)

drivers/hwmon/ad7418.c - no error handling so trivial
drivers/hwmon/ads1015.c - correct
drivers/hwmon/asb100.c - no error handling so trivial
drivers/hwmon/ds1621.c - correct
drivers/hwmon/ds620.c - no error handling so trivial
drivers/hwmon/gl518sm.c - no error handling so trivial
drivers/hwmon/gl520sm.c - no error handling so trivial
drivers/hwmon/jc42.c - correct
drivers/hwmon/lm73.c - no error handling
drivers/hwmon/lm75.c - correct
drivers/hwmon/lm92.c - some are byte swapped. Implementation doesn't handle errors
drivers/hwmon/tmp102.c - correct
drivers/hwmon/w83781.c - no error handling.
drivers/input/touchscreen/ad7879-i2c.c - no error handling
drivers/media/video/mt9m001.c - correct
drivers/media/video/mt9m111.c - no error handling
drivers/media/video/mt9t031.c - correct
drivers/media/video/mt9v022.c - correct
drivers/media/video/mt9v032.c - correct
drivers/media/video/vpx3220.c - correct
drivers/staging/iio/adc/ad7150.c - correct
drivers/staging/iio/adc/ad7152.c - correct
drivers/staging/iio/adc/ad7291.c - correct
drivers/staging/iio/adc/ad7746.c - correct
drivers/staging/iio/adc/ad799x_core.c - correct
drivers/staging/iio/adc/adt7410.c - correct
drivers/staging/iio/adc/adt75.c - correct

'correct' are those that need handle or at least pass on the error code without
mangling it.  The others typically just shove an error into some local
cache without taking any notice.

Just for the curious this is based on greping for i2c_smbus_write_word_data and
looking to see if the read does the swab16 as well.

Anyhow, so to the proposal.  Introduce a couple of inline static functions into
i2c.h.

My only use examples done so far are on top of unpublished iio
changes, so I'll leave the reader to take a look and decided
whether or not this is interesting enough to do.

Even if the driver uses equivalent functions we are saving about
6 lines per user.  I'm happy to do a series converting the easy
ones from the above if people don't mind the patch.

 include/linux/i2c.h |   18 ++++++++++++++++++
 1 files changed, 18 insertions(+), 0 deletions(-)

diff --git a/include/linux/i2c.h b/include/linux/i2c.h
index a6c652e..59ae02b 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>
 
 extern struct bus_type i2c_bus_type;
 extern struct device_type i2c_adapter_type;
@@ -88,6 +89,23 @@ 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_data_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_data_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);
-- 
1.7.3.4