1.. SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
2
3.. _devlink_flash:
4
5=============
6Devlink Flash
7=============
8
9The ``devlink-flash`` API allows updating device firmware. It replaces the
10older ``ethtool-flash`` mechanism, and doesn't require taking any
11networking locks in the kernel to perform the flash update. Example use::
12
13  $ devlink dev flash pci/0000:05:00.0 file flash-boot.bin
14
15Note that the file name is a path relative to the firmware loading path
16(usually ``/lib/firmware/``). Drivers may send status updates to inform
17user space about the progress of the update operation.
18
19Firmware Loading
20================
21
22Devices which require firmware to operate usually store it in non-volatile
23memory on the board, e.g. flash. Some devices store only basic firmware on
24the board, and the driver loads the rest from disk during probing.
25``devlink-info`` allows users to query firmware information (loaded
26components and versions).
27
28In other cases the device can both store the image on the board, load from
29disk, or automatically flash a new image from disk. The ``fw_load_policy``
30devlink parameter can be used to control this behavior
31(:ref:`Documentation/networking/devlink/devlink-params.rst <devlink_params_generic>`).
32
33On-disk firmware files are usually stored in ``/lib/firmware/``.
34
35Firmware Version Management
36===========================
37
38Drivers are expected to implement ``devlink-flash`` and ``devlink-info``
39functionality, which together allow for implementing vendor-independent
40automated firmware update facilities.
41
42``devlink-info`` exposes the ``driver`` name and three version groups
43(``fixed``, ``running``, ``stored``).
44
45The ``driver`` attribute and ``fixed`` group identify the specific device
46design, e.g. for looking up applicable firmware updates. This is why
47``serial_number`` is not part of the ``fixed`` versions (even though it
48is fixed) - ``fixed`` versions should identify the design, not a single
49device.
50
51``running`` and ``stored`` firmware versions identify the firmware running
52on the device, and firmware which will be activated after reboot or device
53reset.
54
55The firmware update agent is supposed to be able to follow this simple
56algorithm to update firmware contents, regardless of the device vendor:
57
58.. code-block:: sh
59
60  # Get unique HW design identifier
61  $hw_id = devlink-dev-info['fixed']
62
63  # Find out which FW flash we want to use for this NIC
64  $want_flash_vers = some-db-backed.lookup($hw_id, 'flash')
65
66  # Update flash if necessary
67  if $want_flash_vers != devlink-dev-info['stored']:
68      $file = some-db-backed.download($hw_id, 'flash')
69      devlink-dev-flash($file)
70
71  # Find out the expected overall firmware versions
72  $want_fw_vers = some-db-backed.lookup($hw_id, 'all')
73
74  # Update on-disk file if necessary
75  if $want_fw_vers != devlink-dev-info['running']:
76      $file = some-db-backed.download($hw_id, 'disk')
77      write($file, '/lib/firmware/')
78
79  # Try device reset, if available
80  if $want_fw_vers != devlink-dev-info['running']:
81     devlink-reset()
82
83  # Reboot, if reset wasn't enough
84  if $want_fw_vers != devlink-dev-info['running']:
85     reboot()
86
87Note that each reference to ``devlink-dev-info`` in this pseudo-code
88is expected to fetch up-to-date information from the kernel.
89
90For the convenience of identifying firmware files some vendors add
91``bundle_id`` information to the firmware versions. This meta-version covers
92multiple per-component versions and can be used e.g. in firmware file names
93(all component versions could get rather long.)
94