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Jacob Keller 5d5b4128c4 devlink: introduce flash update overwrite mask 
Sections of device flash may contain settings or device identifying
information. When performing a flash update, it is generally expected
that these settings and identifiers are not overwritten.

However, it may sometimes be useful to allow overwriting these fields
when performing a flash update. Some examples include, 1) customizing
the initial device config on first programming, such as overwriting
default device identifying information, or 2) reverting a device
configuration to known good state provided in the new firmware image, or
3) in case it is suspected that current firmware logic for managing the
preservation of fields during an update is broken.

Although some devices are able to completely separate these types of
settings and fields into separate components, this is not true for all
hardware.

To support controlling this behavior, a new
DEVLINK_ATTR_FLASH_UPDATE_OVERWRITE_MASK is defined. This is an
nla_bitfield32 which will define what subset of fields in a component
should be overwritten during an update.

If no bits are specified, or of the overwrite mask is not provided, then
an update should not overwrite anything, and should maintain the
settings and identifiers as they are in the previous image.

If the overwrite mask has the DEVLINK_FLASH_OVERWRITE_SETTINGS bit set,
then the device should be configured to overwrite any of the settings in
the requested component with settings found in the provided image.

Similarly, if the DEVLINK_FLASH_OVERWRITE_IDENTIFIERS bit is set, the
device should be configured to overwrite any device identifiers in the
requested component with the identifiers from the image.

Multiple overwrite modes may be combined to indicate that a combination
of the set of fields that should be overwritten.

Drivers which support the new overwrite mask must set the
DEVLINK_SUPPORT_FLASH_UPDATE_OVERWRITE_MASK in the
supported_flash_update_params field of their devlink_ops.

Signed-off-by: Jacob Keller <jacob.e.keller@intel.com>
Reviewed-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
2020-09-25 17:20:57 -07:00

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.. SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
.. _devlink_flash:
=============
Devlink Flash
=============
The ``devlink-flash`` API allows updating device firmware. It replaces the
older ``ethtool-flash`` mechanism, and doesn't require taking any
networking locks in the kernel to perform the flash update. Example use::
$ devlink dev flash pci/0000:05:00.0 file flash-boot.bin
Note that the file name is a path relative to the firmware loading path
(usually ``/lib/firmware/``). Drivers may send status updates to inform
user space about the progress of the update operation.
Overwrite Mask
==============
The ``devlink-flash`` command allows optionally specifying a mask indicating
how the device should handle subsections of flash components when updating.
This mask indicates the set of sections which are allowed to be overwritten.
.. list-table:: List of overwrite mask bits
:widths: 5 95
* - Name
- Description
* - ``DEVLINK_FLASH_OVERWRITE_SETTINGS``
- Indicates that the device should overwrite settings in the components
being updated with the settings found in the provided image.
* - ``DEVLINK_FLASH_OVERWRITE_IDENTIFIERS``
- Indicates that the device should overwrite identifiers in the
components being updated with the identifiers found in the provided
image. This includes MAC addresses, serial IDs, and similar device
identifiers.
Multiple overwrite bits may be combined and requested together. If no bits
are provided, it is expected that the device only update firmware binaries
in the components being updated. Settings and identifiers are expected to be
preserved across the update. A device may not support every combination and
the driver for such a device must reject any combination which cannot be
faithfully implemented.
Firmware Loading
================
Devices which require firmware to operate usually store it in non-volatile
memory on the board, e.g. flash. Some devices store only basic firmware on
the board, and the driver loads the rest from disk during probing.
``devlink-info`` allows users to query firmware information (loaded
components and versions).
In other cases the device can both store the image on the board, load from
disk, or automatically flash a new image from disk. The ``fw_load_policy``
devlink parameter can be used to control this behavior
(:ref:`Documentation/networking/devlink/devlink-params.rst <devlink_params_generic>`).
On-disk firmware files are usually stored in ``/lib/firmware/``.
Firmware Version Management
===========================
Drivers are expected to implement ``devlink-flash`` and ``devlink-info``
functionality, which together allow for implementing vendor-independent
automated firmware update facilities.
``devlink-info`` exposes the ``driver`` name and three version groups
(``fixed``, ``running``, ``stored``).
The ``driver`` attribute and ``fixed`` group identify the specific device
design, e.g. for looking up applicable firmware updates. This is why
``serial_number`` is not part of the ``fixed`` versions (even though it
is fixed) - ``fixed`` versions should identify the design, not a single
device.
``running`` and ``stored`` firmware versions identify the firmware running
on the device, and firmware which will be activated after reboot or device
reset.
The firmware update agent is supposed to be able to follow this simple
algorithm to update firmware contents, regardless of the device vendor:
.. code-block:: sh
# Get unique HW design identifier
$hw_id = devlink-dev-info['fixed']
# Find out which FW flash we want to use for this NIC
$want_flash_vers = some-db-backed.lookup($hw_id, 'flash')
# Update flash if necessary
if $want_flash_vers != devlink-dev-info['stored']:
$file = some-db-backed.download($hw_id, 'flash')
devlink-dev-flash($file)
# Find out the expected overall firmware versions
$want_fw_vers = some-db-backed.lookup($hw_id, 'all')
# Update on-disk file if necessary
if $want_fw_vers != devlink-dev-info['running']:
$file = some-db-backed.download($hw_id, 'disk')
write($file, '/lib/firmware/')
# Try device reset, if available
if $want_fw_vers != devlink-dev-info['running']:
devlink-reset()
# Reboot, if reset wasn't enough
if $want_fw_vers != devlink-dev-info['running']:
reboot()
Note that each reference to ``devlink-dev-info`` in this pseudo-code
is expected to fetch up-to-date information from the kernel.
For the convenience of identifying firmware files some vendors add
``bundle_id`` information to the firmware versions. This meta-version covers
multiple per-component versions and can be used e.g. in firmware file names
(all component versions could get rather long.)
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