1# smbios-mdr 2 3## SMBIOS Parser 4 5The main application in this repo is `smbiosmdrv2app`, capable of parsing a 6binary [SMBIOS][1] table and publishing the system information on D-Bus, to be 7consumed by other OpenBMC applications. 8 9The SMBIOS table is usually sent to the BMC by the host firmware (BIOS). The 10system designer can theoretically choose any transport and mechanism for sending 11the SMBIOS data, but there are at least two implementation today: 12 13### MDRv2 14 15The primary API is a set of Intel OEM IPMI commands called Managed Data Region 16version 2 (MDRv2), which provides a means for host firmware to send data through 17the VGA shared memory region. MDRv2 has a concept of multiple agents, each 18maintaining a "directory" containing directory entries (aka data sets). The host 19can query for the existence and version of directories to determine when it 20needs to send an updated SMBIOS table. 21 22`intel-ipmi-oem` implements the [IPMI command handlers][2], routing commands and 23data to the correct agent (e.g. `smbios-mdr`). The [D-Bus interface][3] between 24the IPMI handler and `smbios-mdr` is largely a mirror of IPMI commands. 25 26### phosphor-ipmi-blobs 27 28[`phosphor-ipmi-blobs`][4] is an alternative implementation of a generic IPMI 29blob transfer API. Compared to MDRv2, it is simpler and easier to use, but also 30transfers the data in-band with the IPMI commands and therefore slower than 31using a shared memory region (which may or may not be a concern). 32 33`phosphor-ipmi-blobs` provides a blob manager shared library for `ipmid` which 34implements the IPMI commands. In turn, it loads blob handler libraries that each 35implement support for specific blobs. Here in `smbios-mdr` we provide such a 36blob handler for the `/smbios` blob. It works by writing the data into 37`/var/lib/smbios/smbios2` (the local persistent cache for the SMBIOS table) and 38calling the `AgentSynchronizeData` D-Bus method to trigger `smbios-mdr` to 39reload and parse the table from that file. 40 41## Intel CPU Info 42 43`cpuinfoapp` is an Intel-specific application that uses I2C and PECI to gather 44more details about Xeon CPUs that aren't included in the SMBIOS table for some 45reason. It also implements discovery and control for Intel Speed Select 46Technology (SST). 47 48[1]: https://www.dmtf.org/standards/smbios 49[2]: 50 https://github.com/openbmc/intel-ipmi-oem/blob/84c203d2b74680e9dd60d1c48a2f6ca8f58462bf/src/smbiosmdrv2handler.cpp#L1272 51[3]: 52 https://github.com/openbmc/phosphor-dbus-interfaces/blob/d1484a1499bc241316853934e6e8b735166deee2/yaml/xyz/openbmc_project/Smbios/MDR_V2.interface.yaml 53[4]: https://github.com/openbmc/phosphor-ipmi-blobs 54