memdisk/dskprobe.c

   1 /* ----------------------------------------------------------------------- *
   2  *
   3  *   Copyright 2009 Shao Miller - All Rights Reserved
   4  *
   5  *   This program is free software; you can redistribute it and/or modify
   6  *   it under the terms of the GNU General Public License as published by
   7  *   the Free Software Foundation, Inc., 53 Temple Place Ste 330,
   8  *   Boston MA 02111-1307, USA; either version 2 of the License, or
   9  *   (at your option) any later version; incorporated herein by reference.
  10  *
  11  * ----------------------------------------------------------------------- */
  12
  13 /*
  14  * dskprobe.c
  15  *
  16  * Routines for probing BIOS disk drives
  17  */
  18
  19 /* Change to 1 for debugging */
  20 #define DBG_DSKPROBE 0
  21
  22 #include <stdint.h>
  23 #include "memdisk.h"
  24 #include "bda.h"
  25 #include "conio.h"
  26
  27 /* Function type for printf() */
  28 typedef int (f_printf) (const char *, ...);
  29
  30 /* Dummy printf() that does nothing */
  31 static f_printf no_printf;
  32 static f_printf *dskprobe_printfs[] = { no_printf, printf };
  33
  34 #define dskprobe_printf (dskprobe_printfs[DBG_DSKPROBE])
  35
  36 static void dskprobe_pause(com32sys_t *);
  37
  38 /* Probe routine function type */
  39 typedef int (f_probe) (uint8_t, com32sys_t *);
  40 static f_probe probe_int13h_08h, probe_int13h_15h, probe_int13h_41h;
  41
  42 /* We will probe a BIOS drive number using INT 0x13, AH == func */
  43 static void probe_any(uint8_t func, uint8_t drive, com32sys_t * regs)
  44 {
  45     regs->eax.b[1] = func;      /* AH == sub-function for probe */
  46     regs->edx.b[0] = drive;     /* DL == drive number to probe */
  47     intcall(0x13, regs, regs);
  48     return;
  49 }
  50
  51 /**
  52  * INT 0x13, AH == 0x08: Get drive parameters.
  53  */
  54 static int probe_int13h_08h(uint8_t drive, com32sys_t * regs)
  55 {
  56     int present;
  57
  58     memset(regs, 0, sizeof *regs);
  59     probe_any(0x08, drive, regs);
  60     present = !(regs->eflags.l & 1);
  61     dskprobe_printf("  AH08: CF%d BL%02x DL%02x\n", regs->eflags.l & 1,
  62                     regs->ebx.b[0], regs->edx.b[0]);
  63     return present;
  64 }
  65
  66 /**
  67  * INT 0x13, AH == 0x15: Get disk type.
  68  */
  69 static int probe_int13h_15h(uint8_t drive, com32sys_t * regs)
  70 {
  71     int present;
  72
  73     memset(regs, 0, sizeof *regs);
  74     probe_any(0x15, drive, regs);
  75     present = !(regs->eflags.l & 1) && regs->eax.b[1];
  76     dskprobe_printf("  AH15: CF%d AH%02x\n", regs->eflags.l & 1,
  77                     regs->eax.b[1]);
  78     return present;
  79 }
  80
  81 /**
  82  * INT 0x13, AH == 0x41: INT 0x13 extensions installation check.
  83  */
  84 static int probe_int13h_41h(uint8_t drive, com32sys_t * regs)
  85 {
  86     int present;
  87
  88     memset(regs, 0, sizeof *regs);
  89     regs->ebx.w[0] = 0x55AA;    /* BX == 0x55AA */
  90     probe_any(0x41, drive, regs);
  91     present = !(regs->eflags.l & 1);
  92     dskprobe_printf("  AH41: CF%d BX%04x AH%02x DH%02x\n", regs->eflags.l & 1,
  93                     regs->ebx.w[0], regs->eax.b[1], regs->edx.b[1]);
  94     return present;
  95 }
  96
  97 /*
  98  * We will probe the BIOS Data Area and count the drives found there.
  99  * This heuristic then assumes that all drives of 'drive's type are
 100  * found in a contiguous range, and returns 1 if the probed drive
 101  * is less than or equal to the BDA count.
 102  * This particular function's code is derived from code in setup.c by
 103  * H. Peter Anvin.  Please respect that file's copyright for this function
 104  */
 105 int probe_bda_drive(uint8_t drive)
 106 {
 107     int bios_drives;
 108     int err;
 109
 110     if (drive & 0x80) {
 111         bios_drives = rdz_8(BIOS_HD_COUNT);     /* HDD count */
 112     } else {
 113         uint8_t equip = rdz_8(BIOS_EQUIP);
 114         if (equip & 1)
 115             bios_drives = (equip >> 6) + 1;     /* Floppy count */
 116         else
 117             bios_drives = 0;
 118     }
 119     err = (drive - (drive & 0x80)) >= bios_drives ? 0 : 1;
 120     dskprobe_printf("BDA drive %02x? %d, total count: %d\n", drive, err,
 121                     bios_drives);
 122     return err;
 123 }
 124
 125 /*
 126  * We will probe a drive with a few different methods, returning
 127  * the count of succesful probes
 128  */
 129 int multi_probe_drive(uint8_t drive)
 130 {
 131     int c = 0;
 132     com32sys_t regs;
 133
 134     dskprobe_printf("INT 13 DL%02x:\n", drive);
 135     /* Only probe the BDA for floppies */
 136     if (drive & 0x80) {
 137
 138         c += probe_int13h_08h(drive, &regs);
 139         c += probe_int13h_15h(drive, &regs);
 140         c += probe_int13h_41h(drive, &regs);
 141     }
 142     c += probe_bda_drive(drive);
 143     dskprobe_pause(&regs);
 144     return c;
 145 }
 146
 147 /*
 148  * We will probe a contiguous range of BIOS drive, starting with drive
 149  * number 'start'.  We probe with a few different methods, and return
 150  * the first drive which doesn't respond to any of the probes.
 151  */
 152 uint8_t probe_drive_range(uint8_t start)
 153 {
 154     uint8_t drive = start;
 155     while (multi_probe_drive(drive)) {
 156         drive++;
 157         /* Check for passing the floppy/HDD boundary */
 158         if ((drive & 0x7F) == 0)
 159             break;
 160     }
 161     return drive;
 162 }
 163
 164 /* Dummy printf() that does nothing */
 165 static int no_printf(const char *ignored, ...)
 166 {
 167     (void)ignored;
 168     return 0;
 169 }
 170
 171 /* Pause if we are in debug-mode */
 172 static void dskprobe_pause(com32sys_t * regs)
 173 {
 174     if (!DBG_DSKPROBE)
 175         return;
 176     dskprobe_printf("Press a key to continue...\n");
 177     memset(regs, 0, sizeof *regs);
 178     regs->eax.w[0] = 0;
 179     intcall(0x16, regs, NULL);
 180     return;
 181 }