ACPI: thinkpad-acpi: add tablet-mode reporting

A quick study of the 0x5009/0x500A HKEY event on the X61t DSDT revealed the
existence of the EC HTAB register (EC 0x0f, bit 7), and a compare with the
X41t DSDT shows that HKEY.MHKG can be used to verify if the ThinkPad is
tablet-capable (MHKG present), and in tablet mode (bit 3 of MHKG return is
set).

Add an attribute to report this information, "hotkey_tablet_mode".  This
attribute has poll()/select() support, and can be used along with EV_SW
SW_TABLET_MODE to hook userspace to tablet events.

Signed-off-by: Henrique de Moraes Holschuh <hmh@hmh.eng.br>
Signed-off-by: Len Brown <len.brown@intel.com>

1 files changed, 7 insertions, 0 deletions

diff --git a/Documentation/laptops/thinkpad-acpi.txt b/Documentation/laptops/thinkpad-acpi.txt
index 606af1628382..76cb428435da 100644
--- a/Documentation/laptops/thinkpad-acpi.txt
+++ b/Documentation/laptops/thinkpad-acpi.txt
@@ -313,6 +313,13 @@ sysfs notes:
 
                 This attribute has poll()/select() support.
 
+        hotkey_tablet_mode:
+                If the ThinkPad has tablet capabilities, this attribute
+                will read 0 if the ThinkPad is in normal mode, and
+                1 if the ThinkPad is in tablet mode.
+
+                This attribute has poll()/select() support.
+
         hotkey_report_mode:
                 Returns the state of the procfs ACPI event report mode
                 filter for hot keys.  If it is set to 1 (the default),