i2c: core: Allow empty id_table in ACPI case as well

For now empty ID table is not allowed with ACPI and prevents driver to
be probed.

Add a check to allow empty ID table.

This introduces a helper i2c_acpi_match_device().

Note, we rename some static function in i2c-core-acpi.c to distinguish
with public API.

Fixes: da10c06a044b ("i2c: Make I2C ID tables non-mandatory for DT'ed devices")
Signed-off-by: Andy Shevchenko <[e-mail]>
Tested-by: Rajmohan Mani <[e-mail]>
Acked-by: Mika Westerberg <[e-mail]>
[wsa: needed to get some drivers probed again]
Signed-off-by: Wolfram Sang <[e-mail]>

drivers/i2c/i2c-core-acpi.c

···
 		dev_warn(&adap->dev, "failed to enumerate I2C slaves\n");
 }
 
+const struct acpi_device_id *
+i2c_acpi_match_device(const struct acpi_device_id *matches,
+		      struct i2c_client *client)
+{
+	if (!(client && matches))
+		return NULL;
+
+	return acpi_match_device(matches, &client->dev);
+}
+
 static acpi_status i2c_acpi_lookup_speed(acpi_handle handle, u32 level,
 					   void *data, void **return_value)
 {
···
 }
 EXPORT_SYMBOL_GPL(i2c_acpi_find_bus_speed);
 
-static int i2c_acpi_match_adapter(struct device *dev, void *data)
+static int i2c_acpi_find_match_adapter(struct device *dev, void *data)
 {
 	struct i2c_adapter *adapter = i2c_verify_adapter(dev);
 
···
 	return ACPI_HANDLE(dev) == (acpi_handle)data;
 }
 
-static int i2c_acpi_match_device(struct device *dev, void *data)
+static int i2c_acpi_find_match_device(struct device *dev, void *data)
 {
 	return ACPI_COMPANION(dev) == data;
 }
···
 	struct device *dev;
 
 	dev = bus_find_device(&i2c_bus_type, NULL, handle,
-			      i2c_acpi_match_adapter);
+			      i2c_acpi_find_match_adapter);
 	return dev ? i2c_verify_adapter(dev) : NULL;
 }
 
···
 {
 	struct device *dev;
 
-	dev = bus_find_device(&i2c_bus_type, NULL, adev, i2c_acpi_match_device);
+	dev = bus_find_device(&i2c_bus_type, NULL, adev,
+			      i2c_acpi_find_match_device);
 	return dev ? i2c_verify_client(dev) : NULL;
 }
 

drivers/i2c/i2c-core-base.c

···
 	 * Tree match table entry is supplied for the probing device.
 	 */
 	if (!driver->id_table &&
+	    !i2c_acpi_match_device(dev->driver->acpi_match_table, client) &&
 	    !i2c_of_match_device(dev->driver->of_match_table, client))
 		return -ENODEV;
 

drivers/i2c/i2c-core.h

···
 int i2c_check_7bit_addr_validity_strict(unsigned short addr);
 
 #ifdef CONFIG_ACPI
+const struct acpi_device_id *
+i2c_acpi_match_device(const struct acpi_device_id *matches,
+		      struct i2c_client *client);
 void i2c_acpi_register_devices(struct i2c_adapter *adap);
 #else /* CONFIG_ACPI */
 static inline void i2c_acpi_register_devices(struct i2c_adapter *adap) { }
+static inline const struct acpi_device_id *
+i2c_acpi_match_device(const struct acpi_device_id *matches,
+		      struct i2c_client *client)
+{
+	return NULL;
+}
 #endif /* CONFIG_ACPI */
 extern struct notifier_block i2c_acpi_notifier;