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Message-ID: <20110217212821.3967.22439.stgit@mike.mtv.corp.google.com> Date: Thu, 17 Feb 2011 13:28:21 -0800 From: Mike Waychison <mikew@...gle.com> To: Greg KH <greg@...ah.com>, Olof Johansson <olofj@...omium.org>, Andi Kleen <andi@...stfloor.org>, Alan Cox <alan@...rguk.ukuu.org.uk>, Robert Lippert <rlippert@...gle.com> Cc: Jon Mayer <jonmayer@...gle.com>, Duncan Laurie <dlaurie@...gle.com>, Aaron Durbin <adurbin@...gle.com>, linux-kernel@...r.kernel.org, Tim Hockin <thockin@...gle.com>, David Hendrix <dhendrix@...omium.org>, linux-api@...r.kernel.org Subject: [PATCH v1 5/5] firmware: Add documentation for /sys/firmware/dmi Document the new ABI added by the dmi-sysfs module. Signed-off-by: Mike Waychison <mikew@...gle.com> --- Documentation/ABI/testing/sysfs-firmware-dmi | 101 ++++++++++++++++++++++++++ 1 files changed, 101 insertions(+), 0 deletions(-) create mode 100644 Documentation/ABI/testing/sysfs-firmware-dmi diff --git a/Documentation/ABI/testing/sysfs-firmware-dmi b/Documentation/ABI/testing/sysfs-firmware-dmi new file mode 100644 index 0000000..c6526b0 --- /dev/null +++ b/Documentation/ABI/testing/sysfs-firmware-dmi @@ -0,0 +1,101 @@ +What: /sys/firmware/dmi/ +Date: February 2011 +Contact: Mike Waychison <mikew@...gle.com> +Description: + Many machine's firmware (x86 and ia64) export DMI / + SMBIOS tables to the operating system. Getting at this + information is often valuable to userland, especially in + cases where there are OEM extensions used. + + The kernel itself does not rely on the majority of the + information in these tables being correct. It equally + cannot ensure that the data as exported to userland is + without error either. + + DMI is structured as a large table of entries, where + each entry has a common header indicating the type and + length of the entry, as well as 'handle' that is + supposed to be unique amongst all entries. + + Some entries are required by the specification, but many + others are optional. In general though, user's should + never expect to find a specific entry type on their + system unless they know for certain what their firmware + is doing. Machine to machine will vary. + + Multiple entries of the same type are allowed. In order + to handle these duplicate entry types, each entry is + assigned by the operating system an 'instance', which is + derived from an entry type's ordinal position. That is + to say, if there are 'N' multiple entries with the same type + 'T' in the DMI tables (adjacent or spread apart, it + doesn't matter), they will be represented in sysfs as + entries "T-0" through "T-(N-1)": + + Example entry directories: + + /sys/firmware/dmi/entries/17-0 + /sys/firmware/dmi/entries/17-1 + /sys/firmware/dmi/entries/17-2 + /sys/firmware/dmi/entries/17-3 + ... + + Instance numbers are used in lieu of the firmware + assigned entry handles as there is kernel itself makes + no guarantees that handles as exported are unique, and + there are likely firmware images that get this wrong in + the wild. + + Each DMI entry in sysfs has the common header values + exported as attributes: + + handle : The 16bit 'handle' that is assigned to this + entry by the firmware. This handle may be + referred to by other entries. + length : The length of the entry, as presented in the + entry itself. Note that this is _not the + total count of bytes associated with the + entry_. This value represents the length of + the "formatted" portion of the entry. This + "formatted" region is sometimes followed by + the "unformatted" region composed of nul + terminated strings, with termination signalled + by a two nul characters in series. + raw : The raw bytes of the entry. This includes the + "formatted" portion of the entry, the + "unformatted" strings portion of the entry, + and the two terminating nul characters. + + === Entry Specialization === + + Some entry types may have other information available in + sysfs. + + --- Type 15 - System Event Log --- + + This entry allows the firmware to export a log of + events the system has taken. This information is + typically backed by nvram, but the implementation + details are abstracted by this table. This entries data + is exported in the directory: + + /sys/firmware/dmi/entries/15-0/system_event_log + + and has the following attributes (documented in the + SMBIOS / DMI specification under "System Event Log (Type 15)": + + area_length + header_start_offset + data_start_offset + access_method + status + change_token + access_method_address + header_format + per_log_type_descriptor_length + type_descriptors_supported_count + + As well, the kernel exports the binary attribute: + + raw_event_log : The raw binary bits of the event log + as described by the DMI entry. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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