+++ /dev/null
-What: /sys/firmware/dmi/
-Date: February 2011
-Contact: Mike Waychison <mikew@google.com>
-Description:
- Many machines' 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 a firmware-provided
- '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, users 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 experiences 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 the 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.
- type : The type of the entry. This value is the same
- as found in the directory name. It indicates
- how the rest of the entry should be interpreted.
- instance: The instance ordinal of the entry for the
- given type. This value is the same as found
- in the parent directory name.
- position: The ordinal position (zero-based) of the entry
- within the entirety of the DMI entry table.
-
- === Entry Specialization ===
-
- Some entry types may have other information available in
- sysfs. Not all types are specialized.
-
- --- 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 entry's 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.
--- /dev/null
+What: /sys/firmware/dmi/entries/
+Date: February 2011
+Contact: Mike Waychison <mikew@google.com>
+Description:
+ Many machines' 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 a firmware-provided
+ '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, users 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 experiences 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 the 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.
+ type : The type of the entry. This value is the same
+ as found in the directory name. It indicates
+ how the rest of the entry should be interpreted.
+ instance: The instance ordinal of the entry for the
+ given type. This value is the same as found
+ in the parent directory name.
+ position: The ordinal position (zero-based) of the entry
+ within the entirety of the DMI entry table.
+
+ === Entry Specialization ===
+
+ Some entry types may have other information available in
+ sysfs. Not all types are specialized.
+
+ --- 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 entry's 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.
projects / cascardo / linux.git / commitdiff