CEC: Make buffer handling code unit testable

Moving code to common/ to be able to write some unit test. The
API in cec.h will be refactored in a later commit since it does
not look so nice for a common API. However, it is better to do the
refactoring after the unit tests are in place

Signed-off-by: Stefan Adolfsson <sadolfsson@chromium.org>

BUG=b:80288314
BRANCH=none
TEST=emerge-fizz chromeos-ec

Change-Id: I2d675689cc40248d74bf812bd6c86125d681767d
Reviewed-on: https://chromium-review.googlesource.com/1073414
Commit-Ready: Stefan Adolfsson <sadolfsson@chromium.org>
Tested-by: Stefan Adolfsson <sadolfsson@chromium.org>
Reviewed-by: Randall Spangler <rspangler@chromium.org>

1 files changed, 55 insertions, 0 deletions

diff --git a/include/cec.h b/include/cec.h
new file mode 100644
index 0000000000..d16378917f
--- /dev/null
+++ b/include/cec.h
@@ -0,0 +1,55 @@
+/* Copyright 2018 The Chromium OS Authors. All rights reserved.
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#include "ec_commands.h"
+
+/* Size of circular buffer used to store incoming CEC messages */
+#define CEC_CIRCBUF_SIZE 20
+#if CEC_CIRCBUF_SIZE < MAX_CEC_MSG_LEN + 1
+#error "Buffer must fit at least a CEC message and a length byte"
+#endif
+#if CEC_CIRCBUF_SIZE > 255
+#error "Buffer size must not exceed 255 since offsets are uint8_t"
+#endif
+
+/* CEC message during transfer */
+struct cec_msg_transfer {
+	/* The CEC message */
+	uint8_t buf[MAX_CEC_MSG_LEN];
+	/* Bit offset  */
+	uint8_t bit;
+	/* Byte offset */
+	uint8_t byte;
+};
+
+/*
+ * Circular buffer of completed incoming CEC messages
+ * ready to be read out by AP
+ */
+struct cec_rx_cb {
+	/*
+	 * Write offset. Updated from interrupt context when we
+	 * have received a complete message.
+	 */
+	uint8_t write_offset;
+	/* Read offset. Updated when AP sends CEC read command */
+	uint8_t read_offset;
+	/* Cicular buffer data  */
+	uint8_t buf[CEC_CIRCBUF_SIZE];
+};
+
+int msgt_get_bit(const struct cec_msg_transfer *msgt);
+
+void msgt_set_bit(struct cec_msg_transfer *msgt, int val);
+
+void msgt_inc_bit(struct cec_msg_transfer *msgt);
+
+int msgt_is_eom(const struct cec_msg_transfer *msgt, int len);
+
+void rx_circbuf_flush(struct cec_rx_cb *cb);
+
+int rx_circbuf_push(struct cec_rx_cb *cb, uint8_t *msg, uint8_t msg_len);
+
+int rx_circbuf_pop(struct cec_rx_cb *cb, uint8_t *msg, uint8_t *msg_len);