/*
* vdprintf.c
*/
#include <stdio.h>
#include <string.h>
#include <stdarg.h>
#include <unistd.h>
#include <inttypes.h>
#include <sys/io.h>
#include <sys/cpu.h>
#undef DEBUG
#define DEBUG 1
#include <dprintf.h>
#define BUFFER_SIZE 4096
enum serial_port_regs {
THR = 0,
RBR = 0,
DLL = 0,
DLM = 1,
IER = 1,
IIR = 2,
FCR = 2,
LCR = 3,
MCR = 4,
LSR = 5,
MSR = 6,
SCR = 7,
};
#ifndef DEBUG_PORT
# define DEBUG_PORT 0x03f8 /* I/O base address */
#endif
static const uint16_t debug_base = DEBUG_PORT;
static void debug_putc(char c)
{
if (c == '\n')
debug_putc('\r');
while ((inb(debug_base + LSR) & 0x20) == 0)
cpu_relax();
outb(c, debug_base + THR);
}
void vdprintf(const char *format, va_list ap)
{
int rv;
char buffer[BUFFER_SIZE];
char *p;
static bool debug_init = false;
static bool debug_ok = false;
rv = vsnprintf(buffer, BUFFER_SIZE, format, ap);
if (rv < 0)
return;
if (rv > BUFFER_SIZE - 1)
rv = BUFFER_SIZE - 1;
/*
* This unconditionally outputs to a serial port at 0x3f8 regardless of
* if one is enabled or not (this means we don't have to enable the real
* serial console and therefore get conflicting output.)
*/
if (__unlikely(!debug_init)) {
uint8_t dll, dlm, lcr;
debug_init = true;
cli();
/* Initialize the serial port to 115200 n81 with FIFOs enabled */
outb(0x83, debug_base + LCR);
outb(0x01, debug_base + DLL);
outb(0x00, debug_base + DLM);
(void)inb(debug_base + IER); /* Synchronize */
dll = inb(debug_base + DLL);
dlm = inb(debug_base + DLM);
lcr = inb(debug_base + LCR);
outb(0x03, debug_base + LCR);
(void)inb(debug_base + IER); /* Synchronize */
outb(0x00, debug_base + IER);
(void)inb(debug_base + IER); /* Synchronize */
sti();
if (dll != 0x01 || dlm != 0x00 || lcr != 0x83) {
/* No serial port present */
return;
}
outb(0x01, debug_base + FCR);
(void)inb(debug_base + IER); /* Synchronize */
if (inb(debug_base + IIR) < 0xc0) {
outb(0x00, debug_base + FCR); /* Disable non-functional FIFOs */
(void)inb(debug_base + IER); /* Synchronize */
}
debug_ok = true;
}
if (!debug_ok)
return;
p = buffer;
while (rv--)
debug_putc(*p++);
}
