/*
 * Common header file for ESP ("upstream") and FPGA ("downstream")
 * sides of link. This MUST contain only data structures!
 */
#ifndef ESPLINK_H
#define ESPLINK_H 1

#include <stdlib.h>
#include <stdbool.h>
#include <inttypes.h>

#define ESPLINK_HDR_ADDR	((const uint32_t *)0x40000000)

/*
 * Ring buffer descriptor structure; this should be setup time only
 * and is statically cached on the upstream side.
 */
struct esplink_ringbuf_desc {
    struct esplink_ringbuf {
	void *start;
	size_t size;		/* Power of 2 */
    } dstr, ustr;
};

/*
 * Upstream and downstream pointer blocks, with the pointers encoded as
 * offsets into the buffer.
 *
 * Note that the head and tail pointers are reversed between the two
 * directions to allow one to be copied to the other.
 */
struct esplink_ptrs_ustr {
    size_t head;
    size_t tail;
};
struct esplink_ptrs_dstr {
    size_t tail;
    size_t head;
};

#define ESPLINK_HEAD_MAGIC	0x3648dec4
struct esplink_head {
    volatile uint32_t magic;
    uint32_t          hlen;
    struct {
	union {
	    uint32_t    cfg;
	    struct {
		uint8_t fixes;
		uint8_t minor;
		uint8_t major;
		uint8_t fpga;
	    };
	};
    } board;
    const char *signature;
    uint32_t    signature_len;

    struct esplink_ringbuf_head {
	uint32_t count;
	struct esplink_ringbuf_desc *desc;
	struct esplink_ptrs_dstr *dstr; /* Downstream (FPGA) side */
	struct esplink_ptrs_ustr *ustr; /* Upstream (ESP32) side */
    } rb;
};

#define EL_DIRQ_UNDERRUN	0	/* Local interrupt/status bit */
#define EL_DIRQ_HELLO		1
#define EL_DIRQ_RINGBUF		2

#define EL_UIRQ_WREN		0	/* Remote write enable bit, not IRQ */
#define EL_UIRQ_READY		1
#define EL_UIRQ_RINGBUF		2

/*
 * Well known ring buffer indicies; must match for both sides.
 * Currently assuming one link in each direction; if only a unidirectional
 * link is needed, leave the descriptor for the unused direction blank.
 */
enum esplink_ringbuf_user {
    EL_RB_CONFIG,

    EL_RB_COUNT
};

#endif	/* ESPLINK_H */