platform/chrome: wilco_ec: Add support for raw commands in debugfs

Add a debugfs attribute that allows sending raw commands to the EC.
This is useful for development and debug but should not be enabled
in a production environment.

To test:
Get the EC firmware build date
First send the request command
> echo 00 f0 38 00 03 00 > raw
Then read the result. "12/21/18" is in the middle of the response
> cat raw
00 31 32 2f 32 31 2f 31 38 00 00 0f 01 00 01 00  .12/21/18.......

Get the EC firmware build date
First send the request command
> echo 00 f0 38 00 03 00 > raw
Then read the result. "12/21/18" is in the middle of the response
> cat raw
00 31 32 2f 32 31 2f 31 38 00 00 0f 01 00 01 00  .12/21/18.......

Signed-off-by: Duncan Laurie <dlaurie@google.com>
Signed-off-by: Nick Crews <ncrews@chromium.org>
[Fix off-by-one error in wilco_ec/debugfs.c]
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Enric Balletbo i Serra <enric.balletbo@collabora.com>

1 files changed, 23 insertions, 0 deletions

diff --git a/Documentation/ABI/testing/debugfs-wilco-ec b/Documentation/ABI/testing/debugfs-wilco-ec
new file mode 100644
index 000000000000..f814f112e213
--- /dev/null
+++ b/Documentation/ABI/testing/debugfs-wilco-ec
@@ -0,0 +1,23 @@
+What:		/sys/kernel/debug/wilco_ec/raw
+Date:		January 2019
+KernelVersion:	5.1
+Description:
+		Write and read raw mailbox commands to the EC.
+
+		For writing:
+		Bytes 0-1 indicate the message type:
+			00 F0 = Execute Legacy Command
+			00 F2 = Read/Write NVRAM Property
+		Byte 2 provides the command code
+		Bytes 3+ consist of the data passed in the request
+
+		At least three bytes are required, for the msg type and command,
+		with additional bytes optional for additional data.
+
+		Example:
+		// Request EC info type 3 (EC firmware build date)
+		$ echo 00 f0 38 00 03 00 > raw
+		// View the result. The decoded ASCII result "12/21/18" is
+		// included after the raw hex.
+		$ cat raw
+		00 31 32 2f 32 31 2f 31 38 00 38 00 01 00 2f 00  .12/21/18.8...