mirror of
https://github.com/RetroPortingToolKit/psxrecomp
synced 2026-10-28 02:56:36 -04:00
Alex Vanderveen
83 lines
3.6 KiB
C
83 lines
3.6 KiB
C
/*
|
|
* psx_link.h -- abstract serial-link endpoint for the SIO1 device.
|
|
*
|
|
* An endpoint is "the far side of the cable" as seen by one SIO1 block:
|
|
* push a finished character onto the wire, poll characters whose delivery
|
|
* cycle has arrived, and exchange the DTR/DSR + RTS/CTS handshake lines.
|
|
*
|
|
* ===== DETERMINISM CONTRACT (load-bearing, do not relax) =====
|
|
* Every op is a pure function of endpoint state and the guest-cycle argument:
|
|
* - no wall-clock, no threads, no socket I/O inside any op;
|
|
* - rx/rx_peek/get_lines are idempotent for a fixed (state, cycle);
|
|
* - characters carry a due_cycle stamped on the GUEST timeline at tx();
|
|
* rx() releases an entry only once now >= due_cycle;
|
|
* - snapshots serialize due_cycle as a DELTA from the passed guest cycle
|
|
* (absolute cycles fork after a clock restore).
|
|
* A future socket backend must ingest bytes on the netplay path at an agreed
|
|
* guest-cycle boundary and stamp due_cycle from the agreed schedule, leaving
|
|
* rx() a pure ring drain. This is what keeps SIO1 rollback/savestate safe.
|
|
*/
|
|
#ifndef PSX_LINK_H
|
|
#define PSX_LINK_H
|
|
|
|
#include <stdint.h>
|
|
|
|
#ifdef __cplusplus
|
|
extern "C" {
|
|
#endif
|
|
|
|
/* Local outputs (set_lines). */
|
|
#define PSX_LINK_DTR (1u << 0) /* local DTR -> peer DSR */
|
|
#define PSX_LINK_RTS (1u << 1) /* local RTS -> peer CTS */
|
|
/* Remote inputs (get_lines). */
|
|
#define PSX_LINK_DSR (1u << 0) /* peer DTR */
|
|
#define PSX_LINK_CTS (1u << 1) /* peer RTS */
|
|
|
|
typedef struct PsxLinkOps {
|
|
/* Shift one finished character onto the wire. `cycle` is the guest cycle
|
|
* at which the transmit shift completed. Returns 1 if the wire took it,
|
|
* 0 if it was discarded (no cable). */
|
|
int (*tx)(void *self, uint8_t byte, uint64_t cycle);
|
|
/* Pop the next character with due_cycle <= `cycle`. Returns 1/0. */
|
|
int (*rx)(void *self, uint8_t *out, uint64_t cycle);
|
|
/* Non-consuming: due_cycle of the oldest queued inbound character.
|
|
* Returns 1 and writes *due, or 0 if the inbound queue is empty. */
|
|
int (*rx_peek)(void *self, uint64_t *due);
|
|
void (*set_lines)(void *self, uint32_t out_lines); /* PSX_LINK_DTR/RTS */
|
|
uint32_t (*get_lines)(void *self); /* PSX_LINK_DSR/CTS */
|
|
int (*connected)(void *self);
|
|
void (*reset)(void *self);
|
|
/* Snapshot: inbound ring + own output lines, due_cycle as delta vs `now`. */
|
|
uint32_t (*snap_bytes)(void *self);
|
|
void (*snap_write)(void *self, uint8_t *p, uint64_t now);
|
|
int (*snap_read)(void *self, const uint8_t *p, uint32_t len,
|
|
uint64_t now);
|
|
} PsxLinkOps;
|
|
|
|
typedef struct PsxLinkEndpoint {
|
|
const PsxLinkOps *ops;
|
|
void *self;
|
|
} PsxLinkEndpoint;
|
|
|
|
/* Ring depth per direction (fixed; overrun at the DEVICE FIFO, not here —
|
|
* at real link rates the wire never holds more than one char in flight). */
|
|
#define PSX_LINK_RING_DEPTH 64u
|
|
|
|
/* No cable: DSR/CTS low, tx discarded, rx never yields. */
|
|
PsxLinkEndpoint *psx_link_null(void);
|
|
/* Self-wired test cable: TX -> own RX, DTR -> own DSR, RTS -> own CTS. */
|
|
PsxLinkEndpoint *psx_link_loopback_create(void);
|
|
void psx_link_loopback_destroy(PsxLinkEndpoint *ep);
|
|
/* Crossover cable between two SIO1 devices:
|
|
* A.TX -> B.RX, A.DTR -> B.DSR, A.RTS -> B.CTS (and mirrored). */
|
|
void psx_link_crossover_create(PsxLinkEndpoint **a, PsxLinkEndpoint **b);
|
|
void psx_link_crossover_destroy(PsxLinkEndpoint *a, PsxLinkEndpoint *b);
|
|
/* Deterministic extra wire delay added to each character at tx(). */
|
|
void psx_link_set_latency_cycles(PsxLinkEndpoint *ep, uint32_t cycles);
|
|
|
|
#ifdef __cplusplus
|
|
}
|
|
#endif
|
|
|
|
#endif /* PSX_LINK_H */
|