1.. SPDX-License-Identifier: GPL-2.0-only
2
3==================================
4PLDM Firmware Flash Update Library
5==================================
6
7``pldmfw`` implements functionality for updating the flash on a device using
8the PLDM for Firmware Update standard
9<https://www.dmtf.org/documents/pmci/pldm-firmware-update-specification-100>.
10
11.. toctree::
12   :maxdepth: 1
13
14   file-format
15   driver-ops
16
17==================================
18Overview of the ``pldmfw`` library
19==================================
20
21The ``pldmfw`` library is intended to be used by device drivers for
22implementing device flash update based on firmware files following the PLDM
23firwmare file format.
24
25It is implemented using an ops table that allows device drivers to provide
26the underlying device specific functionality.
27
28``pldmfw`` implements logic to parse the packed binary format of the PLDM
29firmware file into data structures, and then uses the provided function
30operations to determine if the firmware file is a match for the device. If
31so, it sends the record and component data to the firmware using the device
32specific implementations provided by device drivers. Once the device
33firmware indicates that the update may be performed, the firmware data is
34sent to the device for programming.
35
36Parsing the PLDM file
37=====================
38
39The PLDM file format uses packed binary data, with most multi-byte fields
40stored in the Little Endian format. Several pieces of data are variable
41length, including version strings and the number of records and components.
42Due to this, it is not straight forward to index the record, record
43descriptors, or components.
44
45To avoid proliferating access to the packed binary data, the ``pldmfw``
46library parses and extracts this data into simpler structures for ease of
47access.
48
49In order to safely process the firmware file, care is taken to avoid
50unaligned access of multi-byte fields, and to properly convert from Little
51Endian to CPU host format. Additionally the records, descriptors, and
52components are stored in linked lists.
53
54Performing a flash update
55=========================
56
57To perform a flash update, the ``pldmfw`` module performs the following
58steps
59
601. Parse the firmware file for record and component information
612. Scan through the records and determine if the device matches any record
62   in the file. The first matched record will be used.
633. If the matching record provides package data, send this package data to
64   the device.
654. For each component that the record indicates, send the component data to
66   the device. For each component, the firmware may respond with an
67   indication of whether the update is suitable or not. If any component is
68   not suitable, the update is canceled.
695. For each component, send the binary data to the device firmware for
70   updating.
716. After all components are programmed, perform any final device-specific
72   actions to finalize the update.
73