hwmon: (lm87) Add support for configuration through platform_data

The lm87 driver normally assumes that firmware configured the chip
correctly.  Since this is not always the case, alllow platform code to
set the channel register value via platform_data.  All other
configuration registers can be changed after driver initialisation.
Signed-off-by: Ben Hutchings <bhutchings@solarflare.com>
Signed-off-by: Jean Delvare <khali@linux-fr.org>

Documentation/hwmon/lm87

@@ -65,11 +65,10 @@ The LM87 has four pins which can serve one of two possible functions,
 depending on the hardware configuration.
 
 Some functions share pins, so not all functions are available at the same
-time. Which are depends on the hardware setup. This driver assumes that
-the BIOS configured the chip correctly. In that respect, it differs from
-the original driver (from lm_sensors for Linux 2.4), which would force the
-LM87 to an arbitrary, compile-time chosen mode, regardless of the actual
-chipset wiring.
+time. Which are depends on the hardware setup. This driver normally
+assumes that firmware configured the chip correctly. Where this is not
+the case, platform code must set the I2C client's platform_data to point
+to a u8 value to be written to the channel register.
 
 For reference, here is the list of exclusive functions:
  - in0+in5 (default) or temp3

drivers/hwmon/lm87.c

@@ -21,11 +21,10 @@
  *   http://www.national.com/pf/LM/LM87.html
  *
  * Some functions share pins, so not all functions are available at the same
- * time. Which are depends on the hardware setup. This driver assumes that
- * the BIOS configured the chip correctly. In that respect, it  differs from
- * the original driver (from lm_sensors for Linux 2.4), which would force the
- * LM87 to an arbitrary, compile-time chosen mode, regardless of the actual
- * chipset wiring.
+ * time. Which are depends on the hardware setup. This driver normally
+ * assumes that firmware configured the chip correctly. Where this is not
+ * the case, platform code must set the I2C client's platform_data to point
+ * to a u8 value to be written to the channel register.
  * For reference, here is the list of exclusive functions:
  *  - in0+in5 (default) or temp3
  *  - fan1 (default) or in6
@@ -843,7 +842,13 @@ static void lm87_init_client(struct i2c_client *client)
 {
 	struct lm87_data *data = i2c_get_clientdata(client);
 
+	if (client->dev.platform_data) {
+		data->channel = *(u8 *)client->dev.platform_data;
+		lm87_write_value(client,
+				 LM87_REG_CHANNEL_MODE, data->channel);
+	} else {
 		data->channel = lm87_read_value(client, LM87_REG_CHANNEL_MODE);
+	}
 	data->config = lm87_read_value(client, LM87_REG_CONFIG) & 0x6F;
 
 	if (!(data->config & 0x01)) {