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