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
  34 #ifndef DEBUG_PORT
  35 # define DEBUG_PORT 0x03f8      /* I/O base address */
  36 #endif
  37
  38 static const uint16_t debug_base = DEBUG_PORT;
  39
  40 static void debug_putc(char c)
  41 {
  42     if (c == '\n')
  43         debug_putc('\r');
  44
  45     while ((inb(debug_base + LSR) & 0x20) == 0)
  46         cpu_relax();
  47     outb(c, debug_base + THR);
  48 }
  49
  50 void vdprintf(const char *format, va_list ap)
  51 {
  52     int rv;
  53     char buffer[BUFFER_SIZE];
  54     char *p;
  55     static bool debug_init = false;
  56     static bool debug_ok   = false;
  57
  58     rv = vsnprintf(buffer, BUFFER_SIZE, format, ap);
  59
  60     if (rv < 0)
  61         return;
  62
  63     if (rv > BUFFER_SIZE - 1)
  64         rv = BUFFER_SIZE - 1;
  65
  66     /*
  67      * This unconditionally outputs to a serial port at 0x3f8 regardless of
  68      * if one is enabled or not (this means we don't have to enable the real
  69      * serial console and therefore get conflicting output.)
  70      */
  71     if (__unlikely(!debug_init)) {
  72         uint8_t dll, dlm, lcr;
  73
  74         debug_init = true;
  75
  76         cli();
  77
  78         /* Initialize the serial port to 115200 n81 with FIFOs enabled */
  79         outb(0x83, debug_base + LCR);
  80         outb(0x01, debug_base + DLL);
  81         outb(0x00, debug_base + DLM);
  82         (void)inb(debug_base + IER);    /* Synchronize */
  83         dll = inb(debug_base + DLL);
  84         dlm = inb(debug_base + DLM);
  85         lcr = inb(debug_base + LCR);
  86
  87         outb(0x03, debug_base + LCR);
  88         (void)inb(debug_base + IER);    /* Synchronize */
  89
  90         outb(0x00, debug_base + IER);
  91         (void)inb(debug_base + IER);    /* Synchronize */
  92
  93         sti();
  94
  95         if (dll != 0x01 || dlm != 0x00 || lcr != 0x83) {
  96             /* No serial port present */
  97             return;
  98         }
  99
 100         outb(0x01, debug_base + FCR);
 101         (void)inb(debug_base + IER);    /* Synchronize */
 102         if (inb(debug_base + IIR) < 0xc0) {
 103             outb(0x00, debug_base + FCR); /* Disable non-functional FIFOs */
 104             (void)inb(debug_base + IER);        /* Synchronize */
 105         }
 106
 107         debug_ok = true;
 108     }
 109
 110     if (!debug_ok)
 111         return;
 112
 113     p = buffer;
 114     while (rv--)
 115         debug_putc(*p++);
 116 }