+### NTB Ping Pong Test Client (ntb\_pingpong)
+
+The Ping Pong test client serves as a demonstration to exercise the doorbell
+and scratchpad registers of NTB hardware, and as an example simple NTB client.
+Ping Pong enables the link when started, waits for the NTB link to come up, and
+then proceeds to read and write the doorbell scratchpad registers of the NTB.
+The peers interrupt each other using a bit mask of doorbell bits, which is
+shifted by one in each round, to test the behavior of multiple doorbell bits
+and interrupt vectors. The Ping Pong driver also reads the first local
+scratchpad, and writes the value plus one to the first peer scratchpad, each
+round before writing the peer doorbell register.
+
+Module Parameters:
+
+* unsafe - Some hardware has known issues with scratchpad and doorbell
+ registers. By default, Ping Pong will not attempt to exercise such
+ hardware. You may override this behavior at your own risk by setting
+ unsafe=1.
+* delay\_ms - Specify the delay between receiving a doorbell
+ interrupt event and setting the peer doorbell register for the next
+ round.
+* init\_db - Specify the doorbell bits to start new series of rounds. A new
+ series begins once all the doorbell bits have been shifted out of
+ range.
+* dyndbg - It is suggested to specify dyndbg=+p when loading this module, and
+ then to observe debugging output on the console.
+
+### NTB Tool Test Client (ntb\_tool)
+
+The Tool test client serves for debugging, primarily, ntb hardware and drivers.
+The Tool provides access through debugfs for reading, setting, and clearing the
+NTB doorbell, and reading and writing scratchpads.
+
+The Tool does not currently have any module parameters.
+
+Debugfs Files:
+
+* *debugfs*/ntb\_tool/*hw*/ - A directory in debugfs will be created for each
+ NTB device probed by the tool. This directory is shortened to *hw*
+ below.
+* *hw*/db - This file is used to read, set, and clear the local doorbell. Not
+ all operations may be supported by all hardware. To read the doorbell,
+ read the file. To set the doorbell, write `s` followed by the bits to
+ set (eg: `echo 's 0x0101' > db`). To clear the doorbell, write `c`
+ followed by the bits to clear.
+* *hw*/mask - This file is used to read, set, and clear the local doorbell mask.
+ See *db* for details.
+* *hw*/peer\_db - This file is used to read, set, and clear the peer doorbell.
+ See *db* for details.
+* *hw*/peer\_mask - This file is used to read, set, and clear the peer doorbell
+ mask. See *db* for details.
+* *hw*/spad - This file is used to read and write local scratchpads. To read
+ the values of all scratchpads, read the file. To write values, write a
+ series of pairs of scratchpad number and value
+ (eg: `echo '4 0x123 7 0xabc' > spad`
+ # to set scratchpads `4` and `7` to `0x123` and `0xabc`, respectively).
+* *hw*/peer\_spad - This file is used to read and write peer scratchpads. See
+ *spad* for details.
+