hwmon: (pmbus) Introduce and use write_byte_data callback

Some of the pmbus core functions uses pmbus_write_byte_data, which does
not support driver callbacks for chip specific write operations. This
could potentially influence some specific regulator chips that for
example need a time delay before each data access.

Lets add support for driver callback with _pmbus_write_byte_data.
Signed-off-by: Mårten Lindahl <marten.lindahl@axis.com>
Link: https://lore.kernel.org/r/20220428144039.2464667-2-marten.lindahl@axis.comSigned-off-by: Guenter Roeck <linux@roeck-us.net>

drivers/hwmon/pmbus/pmbus.h

@@ -438,6 +438,8 @@ struct pmbus_driver_info {
 	int (*read_byte_data)(struct i2c_client *client, int page, int reg);
 	int (*read_word_data)(struct i2c_client *client, int page, int phase,
 			      int reg);
+	int (*write_byte_data)(struct i2c_client *client, int page, int reg,
+			      u8 byte);
 	int (*write_word_data)(struct i2c_client *client, int page, int reg,
 			       u16 word);
 	int (*write_byte)(struct i2c_client *client, int page, u8 value);

drivers/hwmon/pmbus/pmbus_core.c

@@ -276,6 +276,24 @@ static int _pmbus_write_word_data(struct i2c_client *client, int page, int reg,
 	return pmbus_write_word_data(client, page, reg, word);
 }
 
+/*
+ * _pmbus_write_byte_data() is similar to pmbus_write_byte_data(), but checks if
+ * a device specific mapping function exists and calls it if necessary.
+ */
+static int _pmbus_write_byte_data(struct i2c_client *client, int page, int reg, u8 value)
+{
+	struct pmbus_data *data = i2c_get_clientdata(client);
+	const struct pmbus_driver_info *info = data->info;
+	int status;
+
+	if (info->write_byte_data) {
+		status = info->write_byte_data(client, page, reg, value);
+		if (status != -ENODATA)
+			return status;
+	}
+	return pmbus_write_byte_data(client, page, reg, value);
+}
+
 int pmbus_update_fan(struct i2c_client *client, int page, int id,
 		     u8 config, u8 mask, u16 command)
 {
@@ -290,7 +308,7 @@ int pmbus_update_fan(struct i2c_client *client, int page, int id,
 
 	to = (from & ~mask) | (config & mask);
 	if (to != from) {
-		rv = pmbus_write_byte_data(client, page,
+		rv = _pmbus_write_byte_data(client, page,
 					   pmbus_fan_config_registers[id], to);
 		if (rv < 0)
 			return rv;
@@ -397,7 +415,7 @@ int pmbus_update_byte_data(struct i2c_client *client, int page, u8 reg,
 	tmp = (rv & ~mask) | (value & mask);
 
 	if (tmp != rv)
-		rv = pmbus_write_byte_data(client, page, reg, tmp);
+		rv = _pmbus_write_byte_data(client, page, reg, tmp);
 
 	return rv;
 }
@@ -912,7 +930,7 @@ static int pmbus_get_boolean(struct i2c_client *client, struct pmbus_boolean *b,
 
 	regval = status & mask;
 	if (regval) {
-		ret = pmbus_write_byte_data(client, page, reg, regval);
+		ret = _pmbus_write_byte_data(client, page, reg, regval);
 		if (ret)
 			goto unlock;
 	}