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authorMike Waychison <mikew@google.com>2011-04-29 20:39:19 -0400
committerGreg Kroah-Hartman <gregkh@suse.de>2011-04-29 21:09:34 -0400
commit74c5b31c6618f01079212332b2e5f6c42f2d6307 (patch)
treef821278fe44849cb10264031159b01c846c7ed9d /Documentation/ABI
parentf548ccd47d608e88d432745091e13f927ced83f7 (diff)
driver: Google EFI SMI
The "gsmi" driver bridges userland with firmware specific routines for accessing hardware. Currently, this driver only supports NVRAM and eventlog information. Deprecated functions have been removed from the driver, though their op-codes are left in place so that they are not re-used. This driver works by trampolining into the firmware via the smi_command outlined in the FADT table. Three protocols are used due to various limitations over time, but all are included herein. This driver should only ever load on Google boards, identified by either a "Google, Inc." board vendor string in DMI, or "GOOGLE" in the OEM strings of the FADT ACPI table. This logic happens in gsmi_system_valid(). Signed-off-by: Duncan Laurie <dlaurie@google.com> Signed-off-by: Aaron Durbin <adurbin@google.com> Signed-off-by: Mike Waychison <mikew@google.com> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
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1What: /sys/firmware/gsmi
2Date: March 2011
3Contact: Mike Waychison <mikew@google.com>
4Description:
5 Some servers used internally at Google have firmware
6 that provides callback functionality via explicit SMI
7 triggers. Some of the callbacks are similar to those
8 provided by the EFI runtime services page, but due to
9 historical reasons this different entry-point has been
10 used.
11
12 The gsmi driver implements the kernel's abstraction for
13 these firmware callbacks. Currently, this functionality
14 is limited to handling the system event log and getting
15 access to EFI-style variables stored in nvram.
16
17 Layout:
18
19 /sys/firmware/gsmi/vars:
20
21 This directory has the same layout (and
22 underlying implementation as /sys/firmware/efi/vars.
23 See Documentation/ABI/*/sysfs-firmware-efi-vars
24 for more information on how to interact with
25 this structure.
26
27 /sys/firmware/gsmi/append_to_eventlog - write-only:
28
29 This file takes a binary blob and passes it onto
30 the firmware to be timestamped and appended to
31 the system eventlog. The binary format is
32 interpreted by the firmware and may change from
33 platform to platform. The only kernel-enforced
34 requirement is that the blob be prefixed with a
35 32bit host-endian type used as part of the
36 firmware call.
37
38 /sys/firmware/gsmi/clear_config - write-only:
39
40 Writing any value to this file will cause the
41 entire firmware configuration to be reset to
42 "factory defaults". Callers should assume that
43 a reboot is required for the configuration to be
44 cleared.
45
46 /sys/firmware/gsmi/clear_eventlog - write-only:
47
48 This file is used to clear out a portion/the
49 whole of the system event log. Values written
50 should be values between 1 and 100 inclusive (in
51 ASCII) representing the fraction of the log to
52 clear. Not all platforms support fractional
53 clearing though, and this writes to this file
54 will error out if the firmware doesn't like your
55 submitted fraction.
56
57 Callers should assume that a reboot is needed
58 for this operation to complete.