Return values for functions reading/writing manufacturer specific registers are
poorly explained. Add comments to improve documentation.
Signed-off-by: Guenter Roeck <guenter.roeck@xxxxxxxxxxxx>
---
drivers/hwmon/pmbus/pmbus.h | 18 ++++++++++++++++--
1 files changed, 16 insertions(+), 2 deletions(-)
diff --git a/drivers/hwmon/pmbus/pmbus.h b/drivers/hwmon/pmbus/pmbus.h
index a6ae20f..da90167 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.
+ * Function 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);
--
1.7.3.1
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