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#include <kernel/arch/amd64/driver/serial.h>
#include <kernel/arch/amd64/driver/util.h>
#include <kernel/arch/amd64/interrupts.h>
#include <kernel/arch/amd64/port_io.h>
#include <kernel/panic.h>
#include <kernel/proc.h>
#include <kernel/util.h>
#include <stdint.h>
static volatile uint8_t backlog_buf[64];
static volatile ring_t backlog = {(void*)backlog_buf, sizeof backlog_buf, 0, 0};
static const int COM1 = 0x3f8;
static bool COM1_exists = false;
static void accept(VfsReq *req);
static void serial_irq(void);
static VfsReq *hung_reads = NULL;
void serial_init(void) {
if (COM1_exists) {
vfs_root_register("/kdev/com1", accept);
}
}
static bool serial_selftest(void) {
port_out8(COM1 + 4, 0b00011110); // enable loopback mode
for (int i = 0; i < 16; i++) {
port_out8(COM1, i);
if (port_in8(COM1) != i) {
return false;
}
}
return true;
}
void serial_preinit(void) {
irq_fn[IRQ_COM1] = serial_irq;
// 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 (???)
if (serial_selftest()) {
COM1_exists = true;
port_out8(COM1 + 4, 0b00001111); // enable everything in the MCR
}
}
static void serial_irq(void) {
ring_put1b((void*)&backlog, port_in8(COM1));
postqueue_ringreadall(&hung_reads, (void*)&backlog);
}
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(VfsReq *req) {
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:
postqueue_join(&hung_reads, req);
postqueue_ringreadall(&hung_reads, (void*)&backlog);
break;
case VFSOP_WRITE:
if (req->caller && !req->flags) {
char buf[4096];
size_t len = min(sizeof buf, req->input.len);
len = pcpy_from(req->caller, buf, req->input.buf, len);
serial_write(buf, len);
ret = len;
} else {
ret = -1;
}
vfsreq_finish_short(req, ret);
break;
default:
vfsreq_finish_short(req, -1);
break;
}
}
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