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>

diff --git a/Documentation/ABI/testing/sysfs-driver-ppi b/Documentation/ABI/testing/sysfs-driver-ppi
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+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.