cmux.h

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/*
 * Copyright (c) 2022 Trackunit Corporation
 *
 * SPDX-License-Identifier: Apache-2.0
 */
 
/*
 * This library uses CMUX to create multiple data channels, called DLCIs, on a single serial bus.
 * Each DLCI has an address from 1 to 63. DLCI address 0 is reserved for control commands.
 *
 * Design overview:
 *
 *     DLCI1 <-----------+                              +-------> DLCI1
 *                       v                              v
 *     DLCI2 <---> CMUX instance <--> Serial bus <--> Client <--> DLCI2
 *                       ^                              ^
 *     DLCI3 <-----------+                              +-------> DLCI3
 *
 * Writing to and from the CMUX instances is done using the modem_pipe API.
 */
 
#include <zephyr/kernel.h>
#include <zephyr/types.h>
#include <zephyr/sys/ring_buffer.h>
#include <zephyr/sys/atomic.h>
 
#include <zephyr/modem/pipe.h>
 
#ifndef ZEPHYR_MODEM_CMUX_
#define ZEPHYR_MODEM_CMUX_
 
#ifdef __cplusplus
extern "C" {
#endif
 
struct modem_cmux;
 
enum modem_cmux_event {
        MODEM_CMUX_EVENT_CONNECTED = 0,
        MODEM_CMUX_EVENT_DISCONNECTED,
};
 
typedef void (*modem_cmux_callback)(struct modem_cmux *cmux, enum modem_cmux_event event,
                                    void *user_data);
 
enum modem_cmux_state {
        MODEM_CMUX_STATE_DISCONNECTED = 0,
        MODEM_CMUX_STATE_CONNECTING,
        MODEM_CMUX_STATE_CONNECTED,
        MODEM_CMUX_STATE_DISCONNECTING,
};
 
enum modem_cmux_receive_state {
        MODEM_CMUX_RECEIVE_STATE_SOF = 0,
        MODEM_CMUX_RECEIVE_STATE_RESYNC,
        MODEM_CMUX_RECEIVE_STATE_ADDRESS,
        MODEM_CMUX_RECEIVE_STATE_ADDRESS_CONT,
        MODEM_CMUX_RECEIVE_STATE_CONTROL,
        MODEM_CMUX_RECEIVE_STATE_LENGTH,
        MODEM_CMUX_RECEIVE_STATE_LENGTH_CONT,
        MODEM_CMUX_RECEIVE_STATE_DATA,
        MODEM_CMUX_RECEIVE_STATE_FCS,
        MODEM_CMUX_RECEIVE_STATE_DROP,
        MODEM_CMUX_RECEIVE_STATE_EOF,
};
 
enum modem_cmux_dlci_state {
        MODEM_CMUX_DLCI_STATE_CLOSED,
        MODEM_CMUX_DLCI_STATE_OPENING,
        MODEM_CMUX_DLCI_STATE_OPEN,
        MODEM_CMUX_DLCI_STATE_CLOSING,
};
 
struct modem_cmux_dlci {
        sys_snode_t node;
 
        /* Pipe */
        struct modem_pipe pipe;
 
        /* Context */
        uint16_t dlci_address;
        struct modem_cmux *cmux;
 
        /* Receive buffer */
        struct ring_buf receive_rb;
        struct k_mutex receive_rb_lock;
 
        /* Work */
        struct k_work_delayable open_work;
        struct k_work_delayable close_work;
 
        /* State */
        enum modem_cmux_dlci_state state;
};
 
struct modem_cmux_frame {
        uint16_t dlci_address;
        bool cr;
        bool pf;
        uint8_t type;
        const uint8_t *data;
        uint16_t data_len;
};
 
struct modem_cmux_work {
        struct k_work_delayable dwork;
        struct modem_cmux *cmux;
};
 
struct modem_cmux {
        /* Bus pipe */
        struct modem_pipe *pipe;
 
        /* Event handler */
        modem_cmux_callback callback;
        void *user_data;
 
        /* DLCI channel contexts */
        sys_slist_t dlcis;
 
        /* State */
        enum modem_cmux_state state;
        bool flow_control_on;
 
        /* Receive state*/
        enum modem_cmux_receive_state receive_state;
 
        /* Receive buffer */
        uint8_t *receive_buf;
        uint16_t receive_buf_size;
        uint16_t receive_buf_len;
 
        uint8_t work_buf[CONFIG_MODEM_CMUX_WORK_BUFFER_SIZE];
 
        /* Transmit buffer */
        struct ring_buf transmit_rb;
        struct k_mutex transmit_rb_lock;
 
        /* Received frame */
        struct modem_cmux_frame frame;
        uint8_t frame_header[5];
        uint16_t frame_header_len;
 
        /* Work */
        struct k_work_delayable receive_work;
        struct k_work_delayable transmit_work;
        struct k_work_delayable connect_work;
        struct k_work_delayable disconnect_work;
 
        /* Synchronize actions */
        struct k_event event;
};
 
struct modem_cmux_config {
        modem_cmux_callback callback;
        void *user_data;
        uint8_t *receive_buf;
        uint16_t receive_buf_size;
        uint8_t *transmit_buf;
        uint16_t transmit_buf_size;
};
 
void modem_cmux_init(struct modem_cmux *cmux, const struct modem_cmux_config *config);
 
struct modem_cmux_dlci_config {
        uint8_t dlci_address;
        uint8_t *receive_buf;
        uint16_t receive_buf_size;
};
 
struct modem_pipe *modem_cmux_dlci_init(struct modem_cmux *cmux, struct modem_cmux_dlci *dlci,
                                        const struct modem_cmux_dlci_config *config);
 
int modem_cmux_attach(struct modem_cmux *cmux, struct modem_pipe *pipe);
 
int modem_cmux_connect(struct modem_cmux *cmux);
 
int modem_cmux_connect_async(struct modem_cmux *cmux);
 
int modem_cmux_disconnect(struct modem_cmux *cmux);
 
int modem_cmux_disconnect_async(struct modem_cmux *cmux);
 
void modem_cmux_release(struct modem_cmux *cmux);
 
#ifdef __cplusplus
}
#endif
 
#endif /* ZEPHYR_MODEM_CMUX_ */