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