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
 19Overwrite Mask
 20==============
 21
 22The ``devlink-flash`` command allows optionally specifying a mask indicating
 23how the device should handle subsections of flash components when updating.
 24This mask indicates the set of sections which are allowed to be overwritten.
 25
 26.. list-table:: List of overwrite mask bits
 27   :widths: 5 95
 28
 29   * - Name
 30     - Description
 31   * - ``DEVLINK_FLASH_OVERWRITE_SETTINGS``
 32     - Indicates that the device should overwrite settings in the components
 33       being updated with the settings found in the provided image.
 34   * - ``DEVLINK_FLASH_OVERWRITE_IDENTIFIERS``
 35     - Indicates that the device should overwrite identifiers in the
 36       components being updated with the identifiers found in the provided
 37       image. This includes MAC addresses, serial IDs, and similar device
 38       identifiers.
 39
 40Multiple overwrite bits may be combined and requested together. If no bits
 41are provided, it is expected that the device only update firmware binaries
 42in the components being updated. Settings and identifiers are expected to be
 43preserved across the update. A device may not support every combination and
 44the driver for such a device must reject any combination which cannot be
 45faithfully implemented.
 46
 47Firmware Loading
 48================
 49
 50Devices which require firmware to operate usually store it in non-volatile
 51memory on the board, e.g. flash. Some devices store only basic firmware on
 52the board, and the driver loads the rest from disk during probing.
 53``devlink-info`` allows users to query firmware information (loaded
 54components and versions).
 55
 56In other cases the device can both store the image on the board, load from
 57disk, or automatically flash a new image from disk. The ``fw_load_policy``
 58devlink parameter can be used to control this behavior
 59(:ref:`Documentation/networking/devlink/devlink-params.rst <devlink_params_generic>`).
 60
 61On-disk firmware files are usually stored in ``/lib/firmware/``.
 62
 63Firmware Version Management
 64===========================
 65
 66Drivers are expected to implement ``devlink-flash`` and ``devlink-info``
 67functionality, which together allow for implementing vendor-independent
 68automated firmware update facilities.
 69
 70``devlink-info`` exposes the ``driver`` name and three version groups
 71(``fixed``, ``running``, ``stored``).
 72
 73The ``driver`` attribute and ``fixed`` group identify the specific device
 74design, e.g. for looking up applicable firmware updates. This is why
 75``serial_number`` is not part of the ``fixed`` versions (even though it
 76is fixed) - ``fixed`` versions should identify the design, not a single
 77device.
 78
 79``running`` and ``stored`` firmware versions identify the firmware running
 80on the device, and firmware which will be activated after reboot or device
 81reset.
 82
 83The firmware update agent is supposed to be able to follow this simple
 84algorithm to update firmware contents, regardless of the device vendor:
 85
 86.. code-block:: sh
 87
 88  # Get unique HW design identifier
 89  $hw_id = devlink-dev-info['fixed']
 90
 91  # Find out which FW flash we want to use for this NIC
 92  $want_flash_vers = some-db-backed.lookup($hw_id, 'flash')
 93
 94  # Update flash if necessary
 95  if $want_flash_vers != devlink-dev-info['stored']:
 96      $file = some-db-backed.download($hw_id, 'flash')
 97      devlink-dev-flash($file)
 98
 99  # Find out the expected overall firmware versions
100  $want_fw_vers = some-db-backed.lookup($hw_id, 'all')
101
102  # Update on-disk file if necessary
103  if $want_fw_vers != devlink-dev-info['running']:
104      $file = some-db-backed.download($hw_id, 'disk')
105      write($file, '/lib/firmware/')
106
107  # Try device reset, if available
108  if $want_fw_vers != devlink-dev-info['running']:
109     devlink-reset()
110
111  # Reboot, if reset wasn't enough
112  if $want_fw_vers != devlink-dev-info['running']:
113     reboot()
114
115Note that each reference to ``devlink-dev-info`` in this pseudo-code
116is expected to fetch up-to-date information from the kernel.
117
118For the convenience of identifying firmware files some vendors add
119``bundle_id`` information to the firmware versions. This meta-version covers
120multiple per-component versions and can be used e.g. in firmware file names
121(all component versions could get rather long.)