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| -rw-r--r-- | Documentation/drivers/cbfs_smbios.md | 78 |
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diff --git a/Documentation/drivers/cbfs_smbios.md b/Documentation/drivers/cbfs_smbios.md index 54b7ca4179..b11f64cf08 100644 --- a/Documentation/drivers/cbfs_smbios.md +++ b/Documentation/drivers/cbfs_smbios.md @@ -3,6 +3,84 @@ The document describes the coreboot options how to make CBFS files populate platform-unique SMBIOS data. +## SMBIOS Serial Number + +The [DMTF SMBIOS specification] defines a field in the type 1 System +Information and type 2 Baseboard Information called Serial Number. It +is a null-terminated string field assumed to be unique per platform. Certain +mainboard ports have SMBIOS hooks to generate the Serial Numbers from external +data, e.g. Lenovo Thinkpads (see DRIVER_LENOVO_SERIALS). This driver aims to +provide an option to populate the Serial Numbers from CBFS for boards that +can't generate the it from any source. + +### Usage + +In the coreboot configuration menu (`make menuconfig`) go to `Generic Drivers` +and select an option `Serial number in CBFS`. The Kconfig system will enable +`DRIVERS_GENERIC_CBFS_SERIAL` and the relevant code parts will be compiled into +coreboot image. + +After the coreboot build for your board completes, use the cbfstool to include +the file containing the serial number: + +```shell +./build/cbfstool build/coreboot.rom add -n serial_number -t raw -f /path/to/serial_file.txt +``` + +Where `serial_file.txt` is the unterminated string representation of the SMBIOS +type 1 or type 2 Serial Number, e.g. `5Q4Q7Y1`. If you use vboot with 1 or 2 RW +partitions you will have to specify the RW regions where the file is going to +be added too. By default the RW CBFS partitions are truncated, so the files +would probably not fit, one needs to expand them first. + +```shell +./build/cbfstool build/coreboot.rom expand -r FW_MAIN_A +./build/cbfstool build/coreboot.rom add -n serial_number -t raw \ + -f /path/to/serial_file.txt -r FW_MAIN_A +./build/cbfstool build/coreboot.rom truncate -r FW_MAIN_A + +./build/cbfstool build/coreboot.rom expand -r FW_MAIN_B +./build/cbfstool build/coreboot.rom add -n serial_number -t raw \ + -f /path/to/serial_file.txt -r FW_MAIN_B +./build/cbfstool build/coreboot.rom truncate -r FW_MAIN_B +``` + +By default cbfstool adds files to COREBOOT region only, so when vboot is +enabled and the platform is booting from RW partition, the file would not be +picked up by the driver. + +One may retrieve the Serial Number from running system (if it exists) using one +of the following commands: + +```shell +# Type 1 +echo -n `sudo dmidecode -s system-serial-number` > serial_file.txt +# OR Type 2 +echo -n `sudo dmidecode -s baseboard-serial-number` > serial_file.txt +``` + +Ensure the file does not end with whitespaces like LF and/or CR. The above +commands will not add any whitespaces. The driver automatically terminates the +Serial Number with the NULL character. If the CBFS file is not present, the +driver will fall back to the string defined in `MAINBOARD_SERIAL_NUMBER` build +option. + +Please note that this driver provides `smbios_mainboard_serial_number` hook +overriding the default implementation which returns `MAINBOARD_SERIAL_NUMBER` +build option. If you wish to populate only type 2 Serial Number field your +board code needs to implement `smbios_system_serial_number`, otherwise the weak +implementation of `smbios_system_serial_number` will call +`smbios_mainboard_serial_number` from the `DRIVERS_GENERIC_CBFS_SERIAL` +implementation overriding it. So selecting the `DRIVERS_GENERIC_CBFS_SERIAL` +has a side-effect of populating both SMBIOS type 1 and type 2 Serial Numbers +if the board does not implement its own `smbios_system_serial_number`. + +There is also SMBIOS type 3 Chassis Information Serial Number, but it is not +populated by `DRIVERS_GENERIC_CBFS_SERIAL` nor by the default weak +implementation (returns empty string). If you wish to populate type 3 Serial +Number, your board code should override the default +`smbios_chassis_serial_number` weak implementation. + ## SMBIOS System UUID The [DMTF SMBIOS specification] defines a field in the type 1 System |