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#include <kernel/arch/i386/driver/serial.h>
#include <kernel/arch/i386/interrupts/irq.h>
#include <kernel/arch/i386/port_io.h>
#include <kernel/mem/virt.h>
#include <kernel/panic.h>
#include <shared/container/ring.h>
#include <shared/mem.h>
#include <stdint.h>
#define BACKLOG_CAPACITY 64
static volatile uint8_t backlog_buf[BACKLOG_CAPACITY];
static volatile ring_t backlog = {(void*)backlog_buf, BACKLOG_CAPACITY, 0, 0};
static const int COM1 = 0x3f8;
static void accept(struct vfs_request *req);
static bool is_ready(struct vfs_backend *self);
static struct vfs_request *blocked_on = NULL;
static struct vfs_backend backend = BACKEND_KERN(is_ready, accept);
void serial_init(void) { vfs_mount_root_register("/com1", &backend); }
static void serial_selftest(void) {
char b = 0x69;
port_out8(COM1 + 4, 0b00011110); // enable loopback mode
port_out8(COM1, b);
assert(port_in8(COM1) == b);
}
void serial_preinit(void) {
// see https://www.sci.muni.cz/docs/pc/serport.txt
// set baud rate divisor
port_out8(COM1 + 3, 0b10000000); // enable DLAB
port_out8(COM1 + 0, 0x01); // divisor = 1 (low byte)
port_out8(COM1 + 1, 0x00); // (high byte)
port_out8(COM1 + 3, 0b00000011); // 8 bits, no parity, one stop bit
port_out8(COM1 + 1, 0x01); // enable the Data Ready IRQ
port_out8(COM1 + 2, 0b11000111); // enable FIFO with 14-bit trigger level (???)
serial_selftest();
port_out8(COM1 + 4, 0b00001111); // enable everything in the MCR
}
void serial_irq(void) {
ring_put1b((void*)&backlog, port_in8(COM1));
if (blocked_on) {
accept(blocked_on);
blocked_on = NULL;
vfs_backend_tryaccept(&backend);
}
}
static void serial_putchar(char c) {
while ((port_in8(COM1 + 5) & 0x20) == 0); // wait for THRE
port_out8(COM1, c);
}
void serial_write(const char *buf, size_t len) {
for (size_t i = 0; i < len; i++)
serial_putchar(buf[i]);
}
static void accept(struct vfs_request *req) {
static char buf[32];
int ret;
bool valid;
switch (req->type) {
case VFSOP_OPEN:
valid = req->input.len == 0;
vfsreq_finish_short(req, valid ? 0 : -1);
break;
case VFSOP_READ:
if (ring_size((void*)&backlog) == 0) {
/* nothing to read, join queue */
assert(!req->postqueue_next);
struct vfs_request **slot = &blocked_on;
while (*slot)
slot = &(*slot)->postqueue_next;
*slot = req;
} else if (req->caller) {
ret = clamp(0, req->output.len, sizeof buf);
ret = ring_get((void*)&backlog, buf, ret);
virt_cpy_to(req->caller->pages, req->output.buf, buf, ret);
vfsreq_finish_short(req, ret);
} else {
vfsreq_finish_short(req, -1);
}
break;
case VFSOP_WRITE:
if (req->caller) {
struct virt_iter iter;
virt_iter_new(&iter, req->input.buf, req->input.len,
req->caller->pages, true, false);
while (virt_iter_next(&iter))
serial_write(iter.frag, iter.frag_len);
ret = iter.prior;
} else ret = -1;
vfsreq_finish_short(req, ret);
break;
default:
vfsreq_finish_short(req, -1);
break;
}
}
static bool is_ready(struct vfs_backend __attribute__((unused)) *self) {
return true;
}
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