From 20fcfe172190704918969695a16cf621e2f4ce25 Mon Sep 17 00:00:00 2001 From: Guenter Roeck Date: Fri, 26 Aug 2011 08:01:51 -0700 Subject: hwmon: (pmbus) Add comments explaining internal driver API return values Return values for functions reading/writing manufacturer specific registers are poorly explained. Add comments to improve documentation. Signed-off-by: Guenter Roeck Acked-by: Jean Delvare --- drivers/hwmon/pmbus/pmbus.h | 18 ++++++++++++++++-- 1 file changed, 16 insertions(+), 2 deletions(-) (limited to 'drivers/hwmon') diff --git a/drivers/hwmon/pmbus/pmbus.h b/drivers/hwmon/pmbus/pmbus.h index a6ae20ffef6b..8751f4073ec2 100644 --- a/drivers/hwmon/pmbus/pmbus.h +++ b/drivers/hwmon/pmbus/pmbus.h @@ -134,8 +134,16 @@ * Semantics: * Virtual registers are all word size. * READ registers are read-only; writes are either ignored or return an error. - * RESET registers are read/write. Reading returns zero (used for detection), - * writing any value causes the associated history to be reset. + * RESET registers are read/write. Reading reset registers returns zero + * (used for detection), writing any value causes the associated history to be + * reset. + * Virtual registers have to be handled in device specific driver code. Chip + * driver code returns non-negative register values if a virtual register is + * supported, or a negative error code if not. The chip driver may return + * -ENODATA or any other error code in this case, though an error code other + * than -ENODATA is handled more efficiently and thus preferred. Either case, + * the calling PMBus core code will abort if the chip driver returns an error + * code when reading or writing virtual registers. */ #define PMBUS_VIRT_BASE 0x100 #define PMBUS_VIRT_READ_TEMP_MIN (PMBUS_VIRT_BASE + 0) @@ -320,6 +328,12 @@ struct pmbus_driver_info { * The following functions map manufacturing specific register values * to PMBus standard register values. Specify only if mapping is * necessary. + * Functions return the register value (read) or zero (write) if + * successful. A return value of -ENODATA indicates that there is no + * manufacturer specific register, but that a standard PMBus register + * may exist. Any other negative return value indicates that the + * register does not exist, and that no attempt should be made to read + * the standard register. */ int (*read_byte_data)(struct i2c_client *client, int page, int reg); int (*read_word_data)(struct i2c_client *client, int page, int reg); -- cgit v1.2.3-59-g8ed1b