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