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Message-ID: <AANLkTi=_8iU+QVTo+bDUjDc=md7E=fW6HpNuf_EFW2Nn@mail.gmail.com> Date: Thu, 17 Feb 2011 13:50:15 -0800 From: Tim Hockin <thockin@...gle.com> To: Mike Waychison <mikew@...gle.com> Cc: 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>, Jon Mayer <jonmayer@...gle.com>, Duncan Laurie <dlaurie@...gle.com>, Aaron Durbin <adurbin@...gle.com>, linux-kernel@...r.kernel.org, David Hendrix <dhendrix@...omium.org>, linux-api@...r.kernel.org Subject: Re: [PATCH v1 5/5] firmware: Add documentation for /sys/firmware/dmi On Thu, Feb 17, 2011 at 1:28 PM, Mike Waychison <mikew@...gle.com> wrote: > 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 / machines' > + 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 users > + 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 s/there is/the/ > + 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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