ACPI: WMI: Add ACPI-WMI mapping driver

The following is an implementation of the Windows Management
Instrumentation (WMI) ACPI interface mapper (PNP0C14).

What it does:

Parses the _WDG method and exports functions to process WMI method calls,
data block query/ set commands (both based on GUID) and does basic event
handling.

How: WMI presents an in kernel interface here (essentially, a minimal
wrapper around ACPI)

(const char *guid assume the 36 character ASCII representation of
a GUID - e.g. 67C3371D-95A3-4C37-BB61-DD47B491DAAB)

wmi_evaluate_method(const char *guid, u8 instance, u32 method_id,
const struct acpi_buffer *in, struct acpi_buffer *out)

wmi_query_block(const char *guid, u8 instance,
struct acpi_buffer *out)

wmi_set_block(const char *guid, u38 instance,
const struct acpi_buffer *in)

wmi_install_notify_handler(acpi_notify_handler handler);

wmi_remove_notify_handler(void);

wmi_get_event_data(u32 event, struct acpi_buffer *out)

wmi_has_guid(const char guid*)

wmi_has_guid() is a helper function to find if a GUID exists or not on the
system (a quick and easy way for WMI dependant drivers to see if the
the method/ block they want exists, since GUIDs are supposed to be unique).

Event handling - allow a WMI based driver to register a notifier handler
for each GUID with WMI. When a notification is sent to a GUID in WMI, the
handler registered with WMI is then called (it is left to the caller to
ask for the WMI event data associated with the GUID, if needed).

What it won't do:

Unicode - The MS article[1] calls for converting between ASCII and Unicode (or
vice versa) if a GUID is marked as "string". This is left up to the calling
driver.

Handle a MOF[1] - the WMI mapper just exports methods, data and events to
userspace. MOF handling is down to userspace.

Userspace interface - this will be added later.

[1] http://www.microsoft.com/whdc/system/pnppwr/wmi/wmi-acpi.mspx

===
ChangeLog
==

v1 (2007-10-02):

* Initial release

v2 (2007-10-05):

* Cleaned up code - split up super "wmi_evaluate_block" -> each external
  symbol now handles its own ACPI calls, rather than handing off to
  a "super" method (and in turn, is a lot simpler to read)
* Added a find_guid() symbol - return true if a given GUID exists on
  the system
* wmi_* functions now return type acpi_status (since they are just
  fancy wrappers around acpi_evaluate_object())
* Removed extra debug code

v3 (2007-10-27)

* More code clean up - now passes checkpatch.pl
* Change data block calls - ref MS spec, method ID is not required for
  them, so drop it from the function parameters.
* Const'ify guid in the function call parameters.
* Fix _WDG buffer handling - copy the data to our own private structure.
* Change WMI from tristate to bool - otherwise the external functions are
  not exported in linux/acpi.h if you try to build WMI as a module.
* Fix more flag comparisons.
* Add a maintainers entry - since I wrote this, I should take the blame
  for it.

v4 (2007-10-30)

* Add missing brace from after fixing checkpatch errors.
* Rewrote event handling - allow external drivers to register with WMI to
  handle WMI events
* Clean up flags and sanitise flag handling

v5 (2007-11-03)

* Add sysfs interface for userspace. Export events over netlink again.
* Remove module left overs, fully convert to built-in driver.
* Tweak in-kernel API to use u8 for instance, since this is what the GUID
  blocks use (so instance cannot be greater than u8).
* Export wmi_get_event_data() for in kernel WMI drivers.

v6 (2007-11-07)

* Split out userspace into a different patch

v7 (2007-11-20)

* Fix driver to handle multiple PNP0C14 devices - store all GUIDs using
  the kernel's built in list functions, and just keep adding to the list
  every time we handle a PNP0C14 devices - GUIDs will always be unique,
  and WMI callers do not know or care about different devices.
* Change WMI event handler registration to use its' own event handling
  struct; we should not pass an acpi_handle down to any WMI based drivers
  - they should be able to function with only the calls provided in WMI.
* Update my e-mail address

v8 (2007-11-28)

* Convert back to a module.
* Update Kconfig to default to building as a module.
* Remove an erroneous printk.
* Simply comments for string flag (since we now leave the handling to the
  caller).

v9 (2007-12-07)

* Add back missing MODULE_DEVICE_TABLE for autoloading
* Checkpatch fixes

v10 (2007-12-12)

* Workaround broken GUIDs declared expensive without a WCxx method.
* Minor cleanups

v11 (2007-12-17)

* More fixing for broken GUIDs declared expensive without a WCxx method.
* Add basic EmbeddedControl region handling.

v12 (2007-12-18)

* Changed EC region handling code, as per Alexey's comments.

v13 (2007-12-27)

* Changed event handling so that we can have one event handler registered
  per GUID, as per Matthew Garrett's suggestion.

v14 (2008-01-12)

* Remove ACPI debug statements

v15 (2008-02-01)

* Replace two remaining 'x == NULL' type tests with '!x'

v16 (2008-02-05)

* Change MAINTAINERS entry, as I am not, and never have been, paid to work
  on WMI
* Remove 'default' line from Kconfig

Signed-off-by: Carlos Corbacho <carlos@strangeworlds.co.uk>
CC: Matthew Garrett <mjg59@srcf.ucam.org>
CC: Alexey Starikovskiy <aystarik@gmail.com>
Signed-off-by: Len Brown <len.brown@intel.com>

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