devlink: Add support for board.serial_number to info_get cb.

Board serial number is a serial number, often available in PCI
*Vital Product Data*.

Also, update devlink-info.rst documentation file.

Cc: Jiri Pirko <[e-mail]>
Cc: Jakub Kicinski <[e-mail]>
Signed-off-by: Vasundhara Volam <[e-mail]>
Reviewed-by: Michael Chan <[e-mail]>
Reviewed-by: Jiri Pirko <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

Documentation/networking/devlink/devlink-info.rst

···
        reported for two ports of the same device or on two hosts of
        a multi-host device should be identical.
 
-       .. note:: ``devlink-info`` API should be extended with a new field
-	  if devices want to report board/product serial number (often
-	  reported in PCI *Vital Product Data* capability).
+   * - ``board.serial_number``
+     - Board serial number of the device.
+
+       This is usually the serial number of the board, often available in
+       PCI *Vital Product Data*.
 
    * - ``fixed``
      - Group for hardware identifiers, and versions of components
···
 ===========
 
 The following extensions could be useful:
-
- - product serial number - NIC boards often get labeled with a board serial
-   number rather than ASIC serial number; it'd be useful to add board serial
-   numbers to the API if they can be retrieved from the device;
 
  - on-disk firmware file names - drivers list the file names of firmware they
    may need to load onto devices via the ``MODULE_FIRMWARE()`` macro. These,

include/net/devlink.h

···
 				   const char *sn);
 int devlink_info_driver_name_put(struct devlink_info_req *req,
 				 const char *name);
+int devlink_info_board_serial_number_put(struct devlink_info_req *req,
+					 const char *bsn);
 int devlink_info_version_fixed_put(struct devlink_info_req *req,
 				   const char *version_name,
 				   const char *version_value);

include/uapi/linux/devlink.h

···
 
 	DEVLINK_ATTR_PORT_FUNCTION,			/* nested */
 
+	DEVLINK_ATTR_INFO_BOARD_SERIAL_NUMBER,	/* string */
+
 	/* add new attributes above here, update the policy in devlink.c */
 
 	__DEVLINK_ATTR_MAX,

net/core/devlink.c

···
 }
 EXPORT_SYMBOL_GPL(devlink_info_serial_number_put);
 
+int devlink_info_board_serial_number_put(struct devlink_info_req *req,
+					 const char *bsn)
+{
+	return nla_put_string(req->msg, DEVLINK_ATTR_INFO_BOARD_SERIAL_NUMBER,
+			      bsn);
+}
+EXPORT_SYMBOL_GPL(devlink_info_board_serial_number_put);
+
 static int devlink_info_version_put(struct devlink_info_req *req, int attr,
 				    const char *version_name,
 				    const char *version_value)