com32/lib/vdprintf.c

   1 /*
   2  * vdprintf.c
   3  */
   4
   5 #include <stdio.h>
   6 #include <string.h>
   7 #include <stdarg.h>
   8 #include <unistd.h>
   9 #include <inttypes.h>
  10 #include <sys/io.h>
  11 #include <sys/cpu.h>
  12
  13 #undef DEBUG
  14 #define DEBUG 1
  15 #include <dprintf.h>
  16
  17 #define BUFFER_SIZE     4096
  18
  19 enum serial_port_regs {
  20     THR = 0,
  21     RBR = 0,
  22     DLL = 0,
  23     DLM = 1,
  24     IER = 1,
  25     IIR = 2,
  26     FCR = 2,
  27     LCR = 3,
  28     MCR = 4,
  29     LSR = 5,
  30     MSR = 6,
  31     SCR = 7,
  32 };
  33 static const uint16_t debug_base = 0x03f8; /* I/O base address */
  34
  35 static void debug_putc(char c)
  36 {
  37     if (c == '\n')
  38         debug_putc('\r');
  39
  40     while ((inb(debug_base + LSR) & 0x20) == 0)
  41         cpu_relax();
  42     outb(c, debug_base + THR);
  43 }
  44
  45 void vdprintf(const char *format, va_list ap)
  46 {
  47     int rv;
  48     char buffer[BUFFER_SIZE];
  49     char *p;
  50     static bool debug_init = false;
  51     static bool debug_ok   = false;
  52
  53     rv = vsnprintf(buffer, BUFFER_SIZE, format, ap);
  54
  55     if (rv < 0)
  56         return;
  57
  58     if (rv > BUFFER_SIZE - 1)
  59         rv = BUFFER_SIZE - 1;
  60
  61     /*
  62      * This unconditionally outputs to a serial port at 0x3f8 regardless of
  63      * if one is enabled or not (this means we don't have to enable the real
  64      * serial console and therefore get conflicting output.)
  65      */
  66     if (__unlikely(!debug_init)) {
  67         uint8_t dll, dlm, lcr;
  68
  69         debug_init = true;
  70
  71         cli();
  72
  73         /* Initialize the serial port to 115200 n81 with FIFOs enabled */
  74         outb(0x83, debug_base + LCR);
  75         outb(0x01, debug_base + DLL);
  76         outb(0x00, debug_base + DLM);
  77         (void)inb(debug_base + IER);    /* Synchronize */
  78         dll = inb(debug_base + DLL);
  79         dlm = inb(debug_base + DLM);
  80         lcr = inb(debug_base + LCR);
  81
  82         outb(0x03, debug_base + LCR);
  83         (void)inb(debug_base + IER);    /* Synchronize */
  84
  85         outb(0x00, debug_base + IER);
  86         (void)inb(debug_base + IER);    /* Synchronize */
  87
  88         sti();
  89
  90         if (dll != 0x01 || dlm != 0x00 || lcr != 0x83) {
  91             /* No serial port present */
  92             return;
  93         }
  94
  95         outb(0x01, debug_base + FCR);
  96         (void)inb(debug_base + IER);    /* Synchronize */
  97         if (inb(debug_base + IIR) < 0xc0) {
  98             outb(0x00, debug_base + FCR); /* Disable non-functional FIFOs */
  99             (void)inb(debug_base + IER);        /* Synchronize */
 100         }
 101
 102         debug_ok = true;
 103     }
 104
 105     if (!debug_ok)
 106         return;
 107
 108     p = buffer;
 109     while (rv--)
 110         debug_putc(*p++);
 111 }