/* 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 the buffer inside the rx queue */
#define CEC_RX_BUFFER_SIZE 20
#if CEC_RX_BUFFER_SIZE < MAX_CEC_MSG_LEN + 1
#error "Buffer must fit at least a CEC message and a length byte"
#endif
#if CEC_RX_BUFFER_SIZE > 255
#error "Buffer size must not exceed 255 since offsets are uint8_t"
#endif

/* CEC message during transfer */
struct cec_msg_transfer {
	/* Bit offset  */
	uint8_t bit;
	/* Byte offset */
	uint8_t byte;
	/* The CEC message */
	uint8_t buf[MAX_CEC_MSG_LEN];
};

/*
 * Queue of completed incoming CEC messages
 * ready to be read out by AP
 */
struct cec_rx_queue {
	/*
	 * 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;
	/* Data buffer */
	uint8_t buf[CEC_RX_BUFFER_SIZE];
};

/**
 * Get the current bit of a CEC message transfer
 *
 * @param queue		Queue to flush
 */
int cec_transfer_get_bit(const struct cec_msg_transfer *transfer);

/**
 * Set the current bit of a CEC message transfer
 *
 * @param transfer	Message transfer to set current bit of
 * @param val		New bit value
 */
void cec_transfer_set_bit(struct cec_msg_transfer *transfer, int val);

/**
 * Make the current bit the next bit in the transfer buffer
 *
 * @param transfer	Message transfer to change current bit of
 */
void cec_transfer_inc_bit(struct cec_msg_transfer *transfer);

/**
 * Check if current bit is an end-of-message bit and if it is set
 *
 * @param transfer	Message transfer to check for end-of-message
 */
int cec_transfer_is_eom(const struct cec_msg_transfer *transfer, int len);

/**
 * Flush all messages from a CEC receive queue
 *
 * @param queue		Queue to flush
 */
void cec_rx_queue_flush(struct cec_rx_queue *queue);

/**
 * Push a CEC message to a CEC receive queue
 *
 * @param queue		Queue to add message to
 */
int cec_rx_queue_push(struct cec_rx_queue *queue, const uint8_t *msg,
		      uint8_t msg_len);

/**
 * Pop a CEC message from a CEC receive queue
 *
 * @param queue		Queue to retrieve message from
 * @param msg		Buffer to store retrieved message in
 * @param msg_len	Number of data bytes in msg
 */
int cec_rx_queue_pop(struct cec_rx_queue *queue, uint8_t *msg,
		     uint8_t *msg_len);