Documentation: sysfs for Physical Presence Interface

Signed-off-by: Xiaoyan Zhang <xiaoyan.zhang@intel.com>
Signed-off-by: Kent Yoder <key@linux.vnet.ibm.com>

Documentation/ABI/testing/sysfs-driver-ppi

+What:		/sys/devices/pnp0/<bus-num>/ppi/
+Date:		August 2012
+Kernel Version:	3.6
+Contact:	xiaoyan.zhang@intel.com
+Description:
+		This folder includes the attributes related with PPI (Physical
+		Presence Interface). Only if TPM is supported by BIOS, this
+		folder makes sence. The folder path can be got by command
+		'find /sys/ -name 'pcrs''. For the detail information of PPI,
+		please refer to the PPI specification from
+		http://www.trustedcomputinggroup.org/
+
+What:		/sys/devices/pnp0/<bus-num>/ppi/version
+Date:		August 2012
+Contact:	xiaoyan.zhang@intel.com
+Description:
+		This attribute shows the version of the PPI supported by the
+		platform.
+		This file is readonly.
+
+What:		/sys/devices/pnp0/<bus-num>/ppi/request
+Date:		August 2012
+Contact:	xiaoyan.zhang@intel.com
+Description:
+		This attribute shows the request for an operation to be
+		executed in the pre-OS environment. It is the only input from
+		the OS to the pre-OS environment. The request should be an
+		integer value range from 1 to 160, and 0 means no request.
+		This file can be read and written.
+
+What:		/sys/devices/pnp0/00:<bus-num>/ppi/response
+Date:		August 2012
+Contact:	xiaoyan.zhang@intel.com
+Description:
+		This attribute shows the response to the most recent operation
+		request it acted upon. The format is "<request> <response num>
+		: <response description>".
+		This file is readonly.
+
+What:		/sys/devices/pnp0/<bus-num>/ppi/transition_action
+Date:		August 2012
+Contact:	xiaoyan.zhang@intel.com
+Description:
+		This attribute shows the platform-specific action that should
+		take place in order to transition to the BIOS for execution of
+		a requested operation. The format is "<action num>: <action
+		description>".
+		This file is readonly.
+
+What:		/sys/devices/pnp0/<bus-num>/ppi/tcg_operations
+Date:		August 2012
+Contact:	xiaoyan.zhang@intel.com
+Description:
+		This attribute shows whether it is allowed to request an
+		operation to be executed in the pre-OS environment by the BIOS
+		for the requests defined by TCG, i.e. requests from 1 to 22.
+		The format is "<request> <status num>: <status description>".
+		This attribute is only supported by PPI version 1.2+.
+		This file is readonly.
+
+What:		/sys/devices/pnp0/<bus-num>/ppi/vs_operations
+Date:		August 2012
+Contact:	xiaoyan.zhang@intel.com
+Description:
+		This attribute shows whether it is allowed to request an
+		operation to be executed in the pre-OS environment by the BIOS
+		for the verdor specific requests, i.e. requests from 128 to
+		255. The format is same with tcg_operations. This attribute
+		is also only supported by PPI version 1.2+.
+		This file is readonly.