chromeec: allow transport implementation to provide buffers for proto v3

Depending on the transport mechanism for proto v3 different bytes
need to be send and/or read before the request and response. Depending
on the software and/or controller interface that requirement leads to
needing to copy data into temporary buffers.  Avoid this by allowing
the transport mechanism to provide the request and response
buffers.

BUG=chrome-os-partner:31148
BRANCH=None
TEST=Built for rush and ryu. Ran on ryu with i2c implementation.
     Also built for rambi to check x86 systems.

Change-Id: I35d4d69bd1fa900fc0cfe3822496f381405bdcb1
Signed-off-by: Patrick Georgi <pgeorgi@chromium.org>
Original-Commit-Id: c7224426e1d0bcf06ed010131a2462a6ca201d8b
Original-Change-Id: Iad6cce566a253ca72e6f5009a97235ece0a6c1b5
Original-Signed-off-by: Aaron Durbin <adurbin@chromium.org>
Original-Reviewed-on: https://chromium-review.googlesource.com/211138
Original-Reviewed-by: Furquan Shaikh <furquan@chromium.org>
Reviewed-on: http://review.coreboot.org/8827
Tested-by: build bot (Jenkins)
Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.org>

1 files changed, 17 insertions, 4 deletions

diff --git a/src/ec/google/chromeec/ec.h b/src/ec/google/chromeec/ec.h
index a1c59b8dc5..e0db8c17ee 100644
--- a/src/ec/google/chromeec/ec.h
+++ b/src/ec/google/chromeec/ec.h
@@ -69,10 +69,23 @@ struct chromeec_command {
 				   * actual received size out */
 };
 
-/* internal standard implementation for EC command protocols. */
-typedef int (*crosec_io_t)(uint8_t *write_bytes, size_t write_size,
-			   uint8_t *read_bytes, size_t read_size,
-			   void *context);
+/*
+ * There are transport level constraints for sending protov3 packets. Because
+ * of this provide a way for the generic protocol layer to request buffers
+ * so that there is zero copying being done through the layers.
+ *
+ * Request the buffer provided the size. If 'req' is non-zero then the
+ * buffer requested is for EC requests. Otherwise it's for responses. Return
+ * non-NULL on success, NULL on error.
+ */
+void *crosec_get_buffer(size_t size, int req);
+
+/*
+ * The lower level transport works on the buffers handed out to the
+ * upper level. Therefore, only the size of the request and response
+ * are required.
+ */
+typedef int (*crosec_io_t)(size_t req_size, size_t resp_size, void *context);
 int crosec_command_proto(struct chromeec_command *cec_command,
 			 crosec_io_t crosec_io, void *context);