driver core: Add comments about returning array counts

The "read array" variants of the device property functions
can be used to return the number of values in an array.
Update the comments to reflect that.

Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

drivers/base/property.c

@@ -62,13 +62,14 @@ EXPORT_SYMBOL_GPL(fwnode_property_present);
  * device_property_read_u8_array - return a u8 array property of a device
  * @dev: Device to get the property of
  * @propname: Name of the property
- * @val: The values are stored here
+ * @val: The values are stored here or %NULL to return the number of values
  * @nval: Size of the @val array
  *
  * Function reads an array of u8 properties with @propname from the device
  * firmware description and stores them to @val if found.
  *
- * Return: %0 if the property was found (success),
+ * Return: number of values if @val was %NULL,
+ *         %0 if the property was found (success),
  *	   %-EINVAL if given arguments are not valid,
  *	   %-ENODATA if the property does not have a value,
  *	   %-EPROTO if the property is not an array of numbers,
@@ -85,13 +86,14 @@ EXPORT_SYMBOL_GPL(device_property_read_u8_array);
  * device_property_read_u16_array - return a u16 array property of a device
  * @dev: Device to get the property of
  * @propname: Name of the property
- * @val: The values are stored here
+ * @val: The values are stored here or %NULL to return the number of values
  * @nval: Size of the @val array
  *
  * Function reads an array of u16 properties with @propname from the device
  * firmware description and stores them to @val if found.
  *
- * Return: %0 if the property was found (success),
+ * Return: number of values if @val was %NULL,
+ *         %0 if the property was found (success),
  *	   %-EINVAL if given arguments are not valid,
  *	   %-ENODATA if the property does not have a value,
  *	   %-EPROTO if the property is not an array of numbers,
@@ -108,13 +110,14 @@ EXPORT_SYMBOL_GPL(device_property_read_u16_array);
  * device_property_read_u32_array - return a u32 array property of a device
  * @dev: Device to get the property of
  * @propname: Name of the property
- * @val: The values are stored here
+ * @val: The values are stored here or %NULL to return the number of values
  * @nval: Size of the @val array
  *
  * Function reads an array of u32 properties with @propname from the device
  * firmware description and stores them to @val if found.
  *
- * Return: %0 if the property was found (success),
+ * Return: number of values if @val was %NULL,
+ *         %0 if the property was found (success),
  *	   %-EINVAL if given arguments are not valid,
  *	   %-ENODATA if the property does not have a value,
  *	   %-EPROTO if the property is not an array of numbers,
@@ -131,13 +134,14 @@ EXPORT_SYMBOL_GPL(device_property_read_u32_array);
  * device_property_read_u64_array - return a u64 array property of a device
  * @dev: Device to get the property of
  * @propname: Name of the property
- * @val: The values are stored here
+ * @val: The values are stored here or %NULL to return the number of values
  * @nval: Size of the @val array
  *
  * Function reads an array of u64 properties with @propname from the device
  * firmware description and stores them to @val if found.
  *
- * Return: %0 if the property was found (success),
+ * Return: number of values if @val was %NULL,
+ *         %0 if the property was found (success),
  *	   %-EINVAL if given arguments are not valid,
  *	   %-ENODATA if the property does not have a value,
  *	   %-EPROTO if the property is not an array of numbers,
@@ -154,13 +158,14 @@ EXPORT_SYMBOL_GPL(device_property_read_u64_array);
  * device_property_read_string_array - return a string array property of device
  * @dev: Device to get the property of
  * @propname: Name of the property
- * @val: The values are stored here
+ * @val: The values are stored here or %NULL to return the number of values
  * @nval: Size of the @val array
  *
  * Function reads an array of string properties with @propname from the device
  * firmware description and stores them to @val if found.
  *
- * Return: %0 if the property was found (success),
+ * Return: number of values if @val was %NULL,
+ *         %0 if the property was found (success),
  *	   %-EINVAL if given arguments are not valid,
  *	   %-ENODATA if the property does not have a value,
  *	   %-EPROTO or %-EILSEQ if the property is not an array of strings,
@@ -170,7 +175,8 @@ int device_property_read_string_array(struct device *dev, const char *propname,
 				      const char **val, size_t nval)
 {
 	return IS_ENABLED(CONFIG_OF) && dev->of_node ?
-		of_property_read_string_array(dev->of_node, propname, val, nval) :
+		(val ? of_property_read_string_array(dev->of_node, propname, val, nval)
+		     : of_property_count_strings(dev->of_node, propname)) :
 		acpi_dev_prop_read(ACPI_COMPANION(dev), propname,
 				   DEV_PROP_STRING, val, nval);
 }
@@ -218,13 +224,14 @@ EXPORT_SYMBOL_GPL(device_property_read_string);
  * fwnode_property_read_u8_array - return a u8 array property of firmware node
  * @fwnode: Firmware node to get the property of
  * @propname: Name of the property
- * @val: The values are stored here
+ * @val: The values are stored here or %NULL to return the number of values
  * @nval: Size of the @val array
  *
  * Read an array of u8 properties with @propname from @fwnode and stores them to
  * @val if found.
  *
- * Return: %0 if the property was found (success),
+ * Return: number of values if @val was %NULL,
+ *         %0 if the property was found (success),
  *	   %-EINVAL if given arguments are not valid,
  *	   %-ENODATA if the property does not have a value,
  *	   %-EPROTO if the property is not an array of numbers,
@@ -243,13 +250,14 @@ EXPORT_SYMBOL_GPL(fwnode_property_read_u8_array);
  * fwnode_property_read_u16_array - return a u16 array property of firmware node
  * @fwnode: Firmware node to get the property of
  * @propname: Name of the property
- * @val: The values are stored here
+ * @val: The values are stored here or %NULL to return the number of values
  * @nval: Size of the @val array
  *
  * Read an array of u16 properties with @propname from @fwnode and store them to
  * @val if found.
  *
- * Return: %0 if the property was found (success),
+ * Return: number of values if @val was %NULL,
+ *         %0 if the property was found (success),
  *	   %-EINVAL if given arguments are not valid,
  *	   %-ENODATA if the property does not have a value,
  *	   %-EPROTO if the property is not an array of numbers,
@@ -268,13 +276,14 @@ EXPORT_SYMBOL_GPL(fwnode_property_read_u16_array);
  * fwnode_property_read_u32_array - return a u32 array property of firmware node
  * @fwnode: Firmware node to get the property of
  * @propname: Name of the property
- * @val: The values are stored here
+ * @val: The values are stored here or %NULL to return the number of values
  * @nval: Size of the @val array
  *
  * Read an array of u32 properties with @propname from @fwnode store them to
  * @val if found.
  *
- * Return: %0 if the property was found (success),
+ * Return: number of values if @val was %NULL,
+ *         %0 if the property was found (success),
  *	   %-EINVAL if given arguments are not valid,
  *	   %-ENODATA if the property does not have a value,
  *	   %-EPROTO if the property is not an array of numbers,
@@ -293,13 +302,14 @@ EXPORT_SYMBOL_GPL(fwnode_property_read_u32_array);
  * fwnode_property_read_u64_array - return a u64 array property firmware node
  * @fwnode: Firmware node to get the property of
  * @propname: Name of the property
- * @val: The values are stored here
+ * @val: The values are stored here or %NULL to return the number of values
  * @nval: Size of the @val array
  *
  * Read an array of u64 properties with @propname from @fwnode and store them to
  * @val if found.
  *
- * Return: %0 if the property was found (success),
+ * Return: number of values if @val was %NULL,
+ *         %0 if the property was found (success),
  *	   %-EINVAL if given arguments are not valid,
  *	   %-ENODATA if the property does not have a value,
  *	   %-EPROTO if the property is not an array of numbers,
@@ -318,13 +328,14 @@ EXPORT_SYMBOL_GPL(fwnode_property_read_u64_array);
  * fwnode_property_read_string_array - return string array property of a node
  * @fwnode: Firmware node to get the property of
  * @propname: Name of the property
- * @val: The values are stored here
+ * @val: The values are stored here or %NULL to return the number of values
  * @nval: Size of the @val array
  *
  * Read an string list property @propname from the given firmware node and store
  * them to @val if found.
  *
- * Return: %0 if the property was found (success),
+ * Return: number of values if @val was %NULL,
+ *         %0 if the property was found (success),
  *	   %-EINVAL if given arguments are not valid,
  *	   %-ENODATA if the property does not have a value,
  *	   %-EPROTO if the property is not an array of strings,