x86/olpc: Add debugfs interface for EC commands

Add a debugfs interface for sending commands to the OLPC
Embedded Controller (EC) and reading the responses.  The EC
provides functionality for machine identification, battery and
AC control, wakeup control, etc.

Having a debugfs interface available is useful for EC
development and debugging.

Based on code by Paul Fox (who also approves of the end result).

Signed-off-by: Daniel Drake <dsd@laptop.org>
Acked-by: Paul Fox <pgf@laptop.org>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Andres Salomon <dilinger@queued.net>
Link: http://lkml.kernel.org/r/20120327150740.667D09D401E@zog.reactivated.net
Signed-off-by: Ingo Molnar <mingo@kernel.org>

1 files changed, 16 insertions, 0 deletions

diff --git a/Documentation/ABI/testing/debugfs-olpc b/Documentation/ABI/testing/debugfs-olpc
new file mode 100644
index 00000000000..bd76cc6d55f
--- /dev/null
+++ b/Documentation/ABI/testing/debugfs-olpc
@@ -0,0 +1,16 @@
+What:           /sys/kernel/debug/olpc-ec/cmd
+Date:           Dec 2011
+KernelVersion:  3.4
+Contact:        devel@lists.laptop.org
+Description:
+
+A generic interface for executing OLPC Embedded Controller commands and
+reading their responses.
+
+To execute a command, write data with the format: CC:N A A A A
+CC is the (hex) command, N is the count of expected reply bytes, and A A A A
+are optional (hex) arguments.
+
+To read the response (if any), read from the generic node after executing
+a command. Hex reply bytes will be returned, *whether or not* they came from
+the immediately previous command.