[PATCH 15/18] i2c: i2c-core-acpi: Add i2c_acpi_dev_name()

[Daniel Scally <djrscally@xxxxxxxxx>]

Some places in the kernel allow users to map resources to a device
using device name (for example, gpiod_lookup_table). Currently
this involves waiting for the i2c_client to have been registered so we
can use dev_name(&client->dev). Adding this function means that we can
achieve the same thing without having to wait to the i2c device.

Signed-off-by: Daniel Scally <djrscally@xxxxxxxxx>
---
Changes since RFC v3:

	- Patch introduced

 drivers/i2c/i2c-core-acpi.c | 14 ++++++++++++++
 include/linux/i2c.h         |  5 +++++
 2 files changed, 19 insertions(+)

diff --git a/drivers/i2c/i2c-core-acpi.c b/drivers/i2c/i2c-core-acpi.c
index 37c510d9347a..d3a653eac79e 100644
--- a/drivers/i2c/i2c-core-acpi.c
+++ b/drivers/i2c/i2c-core-acpi.c
@@ -497,6 +497,20 @@ struct i2c_client *i2c_acpi_new_device(struct device *dev, int index,
 }
 EXPORT_SYMBOL_GPL(i2c_acpi_new_device);
 
+/**
+ * i2c_acpi_dev_name - Construct i2c device name for devs sourced from ACPI
+ * @adev:     ACPI device to construct the name for
+ *
+ * Prefixes "i2c-" to the ACPI device name, for use in i2c_dev_set_name() and
+ * also anywhere else in the kernel that needs to refer to an i2c device by
+ * name but before they have been instantiated.
+ */
+char *i2c_acpi_dev_name(struct acpi_device *adev)
+{
+	return kasprintf(GFP_KERNEL, "i2c-%s", acpi_dev_name(adev));
+}
+EXPORT_SYMBOL_GPL(i2c_acpi_dev_name);
+
 #ifdef CONFIG_ACPI_I2C_OPREGION
 static int acpi_gsb_i2c_read_bytes(struct i2c_client *client,
 		u8 cmd, u8 *data, u8 data_len)
diff --git a/include/linux/i2c.h b/include/linux/i2c.h
index 56622658b215..ab0e505b2ca6 100644
--- a/include/linux/i2c.h
+++ b/include/linux/i2c.h
@@ -995,6 +995,7 @@ bool i2c_acpi_get_i2c_resource(struct acpi_resource *ares,
 u32 i2c_acpi_find_bus_speed(struct device *dev);
 struct i2c_client *i2c_acpi_new_device(struct device *dev, int index,
 				       struct i2c_board_info *info);
+char *i2c_acpi_dev_name(struct acpi_device *adev);
 struct i2c_adapter *i2c_acpi_find_adapter_by_handle(acpi_handle handle);
 #else
 static inline bool i2c_acpi_get_i2c_resource(struct acpi_resource *ares,
@@ -1011,6 +1012,10 @@ static inline struct i2c_client *i2c_acpi_new_device(struct device *dev,
 {
 	return ERR_PTR(-ENODEV);
 }
+static inline char *i2c_acpi_dev_name(struct acpi_device *adev)
+{
+	return NULL;
+}
 static inline struct i2c_adapter *i2c_acpi_find_adapter_by_handle(acpi_handle handle)
 {
 	return NULL;
-- 
2.25.1