i2c: Allow overriding dev_name through board_info

For devices not instantiated through ACPI the i2c-client's device-name
gets set to <busnr>-<addr> by default, e.g. "0-0022" this means that
the device-name is dependent on the order in which the i2c-busses are
enumerated.

In some cases having a predictable constant device-name is desirable,
for example on non device-tree platforms the link between a regulator
and its consumers is specified by the platform code by setting
regulator_init_data.consumers. This array identifies the regulator's
consumers by dev_name and supply(-name). Which requires a constant
dev_name.

This commit adds a dev_name field to i2c_board_info allowing
platform code to set a contstant dev_name so that the device can
be identified by its dev_name in other platform code.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Acked-by: Mark Brown <broonie@kernel.org> (live at ELCE17)
Acked-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com> (live at ELCE17)
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>

drivers/i2c/i2c-core-base.c

@@ -666,10 +666,16 @@ static void i2c_adapter_unlock_bus(struct i2c_adapter *adapter,
 }
 
 static void i2c_dev_set_name(struct i2c_adapter *adap,
-			     struct i2c_client *client)
+			     struct i2c_client *client,
+			     struct i2c_board_info const *info)
 {
 	struct acpi_device *adev = ACPI_COMPANION(&client->dev);
 
+	if (info && info->dev_name) {
+		dev_set_name(&client->dev, "i2c-%s", info->dev_name);
+		return;
+	}
+
 	if (adev) {
 		dev_set_name(&client->dev, "i2c-%s", acpi_dev_name(adev));
 		return;
@@ -766,7 +772,7 @@ i2c_new_device(struct i2c_adapter *adap, struct i2c_board_info const *info)
 	client->dev.of_node = info->of_node;
 	client->dev.fwnode = info->fwnode;
 
-	i2c_dev_set_name(adap, client);
+	i2c_dev_set_name(adap, client, info);
 
 	if (info->properties) {
 		status = device_add_properties(&client->dev, info->properties);

include/linux/i2c.h

@@ -304,6 +304,7 @@ static inline bool i2c_detect_slave_mode(struct device *dev) { return false; }
  * @type: chip type, to initialize i2c_client.name
  * @flags: to initialize i2c_client.flags
  * @addr: stored in i2c_client.addr
+ * @dev_name: Overrides the default <busnr>-<addr> dev_name if set
  * @platform_data: stored in i2c_client.dev.platform_data
  * @archdata: copied into i2c_client.dev.archdata
  * @of_node: pointer to OpenFirmware device node
@@ -328,6 +329,7 @@ struct i2c_board_info {
 	char		type[I2C_NAME_SIZE];
 	unsigned short	flags;
 	unsigned short	addr;
+	const char	*dev_name;
 	void		*platform_data;
 	struct dev_archdata	*archdata;
 	struct device_node *of_node;