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diff --git a/Documentation/driver-api/pldmfw/index.rst b/Documentation/driver-api/pldmfw/index.rst new file mode 100644 index 000000000000..ad2c33ece30f --- /dev/null +++ b/Documentation/driver-api/pldmfw/index.rst @@ -0,0 +1,72 @@ +.. SPDX-License-Identifier: GPL-2.0-only + +================================== +PLDM Firmware Flash Update Library +================================== + +``pldmfw`` implements functionality for updating the flash on a device using +the PLDM for Firmware Update standard +<https://www.dmtf.org/documents/pmci/pldm-firmware-update-specification-100>. + +.. toctree:: + :maxdepth: 1 + + file-format + driver-ops + +================================== +Overview of the ``pldmfw`` library +================================== + +The ``pldmfw`` library is intended to be used by device drivers for +implementing device flash update based on firmware files following the PLDM +firwmare file format. + +It is implemented using an ops table that allows device drivers to provide +the underlying device specific functionality. + +``pldmfw`` implements logic to parse the packed binary format of the PLDM +firmware file into data structures, and then uses the provided function +operations to determine if the firmware file is a match for the device. If +so, it sends the record and component data to the firmware using the device +specific implementations provided by device drivers. Once the device +firmware indicates that the update may be performed, the firmware data is +sent to the device for programming. + +Parsing the PLDM file +===================== + +The PLDM file format uses packed binary data, with most multi-byte fields +stored in the Little Endian format. Several pieces of data are variable +length, including version strings and the number of records and components. +Due to this, it is not straight forward to index the record, record +descriptors, or components. + +To avoid proliferating access to the packed binary data, the ``pldmfw`` +library parses and extracts this data into simpler structures for ease of +access. + +In order to safely process the firmware file, care is taken to avoid +unaligned access of multi-byte fields, and to properly convert from Little +Endian to CPU host format. Additionally the records, descriptors, and +components are stored in linked lists. + +Performing a flash update +========================= + +To perform a flash update, the ``pldmfw`` module performs the following +steps + +1. Parse the firmware file for record and component information +2. Scan through the records and determine if the device matches any record + in the file. The first matched record will be used. +3. If the matching record provides package data, send this package data to + the device. +4. For each component that the record indicates, send the component data to + the device. For each component, the firmware may respond with an + indication of whether the update is suitable or not. If any component is + not suitable, the update is canceled. +5. For each component, send the binary data to the device firmware for + updating. +6. After all components are programmed, perform any final device-specific + actions to finalize the update. |