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  * Determine if the return from probe_int13h_01h indicates a failure; a
  53  * return of zero indicates no known failure.
  54  */
  55 static int probe_int13h_01h_fail(int istatus)
  56 {
  57     int status = 0;
  58
  59     if (istatus >= 256)
  60         status = istatus;
  61     else
  62         switch (istatus) {
  63         case 1: status = istatus;
  64         }
  65     return status;
  66 }
  67
  68 /**
  69  * INT 0x13, AH == 0x01: Get status of last command.
  70  */
  71 static int probe_int13h_01h(uint8_t drive)
  72 {
  73     int status;
  74     com32sys_t regs;
  75
  76     memset(&regs, 0, sizeof regs);
  77     probe_any(0x01, drive, &regs);
  78     status = (regs.eflags.l & 1) * 256 + regs.eax.b[1];
  79     dskprobe_printf("  AH01: CF%d AH%02x", regs.eflags.l & 1, regs.eax.b[1]);
  80     return status;
  81 }
  82
  83 /**
  84  * INT 0x13, AH == 0x08: Get drive parameters.
  85  */
  86 static int probe_int13h_08h(uint8_t drive, com32sys_t * regs)
  87 {
  88     int present;
  89
  90     memset(regs, 0, sizeof *regs);
  91     probe_any(0x08, drive, regs);
  92     dskprobe_printf("  AH08: CF%d AH%02x AL%02x BL%02x DL%02x",
  93                     regs->eflags.l & 1, regs->eax.b[1], regs->eax.b[0],
  94                     regs->ebx.b[0], regs->edx.b[0]);
  95     present = !(regs->eflags.l & 1) && !regs->eax.b[1];
  96     dskprobe_printf("  P%d\n",  present);
  97     return present;
  98 }
  99
 100 /**
 101  * INT 0x13, AH == 0x15: Get disk type.
 102  */
 103 static int probe_int13h_15h(uint8_t drive, com32sys_t * regs)
 104 {
 105     int present;
 106     int status;
 107
 108     memset(regs, 0, sizeof *regs);
 109     probe_any(0x15, drive, regs);
 110     dskprobe_printf("  AH15: CF%d AH%02x AL%02x CX%04x DX%04x",
 111                     regs->eflags.l & 1, regs->eax.b[1], regs->eax.b[0],
 112                     regs->ecx.w[0], regs->edx.w[0]);
 113     present = !(regs->eflags.l & 1) && regs->eax.b[1];
 114     status = probe_int13h_01h(drive);
 115     present = present && !(probe_int13h_01h_fail(status));
 116     dskprobe_printf("  P%d\n",  present);
 117     return present;
 118 }
 119
 120 /**
 121  * INT 0x13, AH == 0x41: INT 0x13 extensions installation check.
 122  */
 123 static int probe_int13h_41h(uint8_t drive, com32sys_t * regs)
 124 {
 125     int present;
 126
 127     memset(regs, 0, sizeof *regs);
 128     regs->ebx.w[0] = 0x55AA;    /* BX == 0x55AA */
 129     probe_any(0x41, drive, regs);
 130     dskprobe_printf("  AH41: CF%d BX%04x AH%02x DH%02x",
 131                     regs->eflags.l & 1, regs->ebx.w[0], regs->eax.b[1],
 132                     regs->edx.b[1]);
 133     present = !(regs->eflags.l & 1) && (regs->ebx.w[0] == 0xAA55);
 134     dskprobe_printf("  P%d\n",  present);
 135     return present;
 136 }
 137
 138 /*
 139  * We will probe the BIOS Data Area and count the drives found there.
 140  * This heuristic then assumes that all drives of 'drive's type are
 141  * found in a contiguous range, and returns 1 if the probed drive
 142  * is less than or equal to the BDA count.
 143  * This particular function's code is derived from code in setup.c by
 144  * H. Peter Anvin.  Please respect that file's copyright for this function
 145  */
 146 int probe_bda_drive(uint8_t drive)
 147 {
 148     int bios_drives;
 149     int err;
 150
 151     if (drive & 0x80) {
 152         bios_drives = rdz_8(BIOS_HD_COUNT);     /* HDD count */
 153     } else {
 154         uint8_t equip = rdz_8(BIOS_EQUIP);
 155         if (equip & 1)
 156             bios_drives = (equip >> 6) + 1;     /* Floppy count */
 157         else
 158             bios_drives = 0;
 159     }
 160     err = (drive - (drive & 0x80)) >= bios_drives ? 0 : 1;
 161     dskprobe_printf("BDA drive %02x? %d, total count: %d\n", drive, err,
 162                     bios_drives);
 163     return err;
 164 }
 165
 166 /*
 167  * We will probe a drive with a few different methods, returning
 168  * the count of succesful probes
 169  */
 170 int multi_probe_drive(uint8_t drive)
 171 {
 172     int c = 0;
 173     com32sys_t regs;
 174
 175     dskprobe_printf("INT 13 DL%02x:\n", drive);
 176     /* Only probe the BDA for floppies */
 177     if (drive & 0x80) {
 178
 179         c += probe_int13h_08h(drive, &regs);
 180         c += probe_int13h_15h(drive, &regs);
 181         c += probe_int13h_41h(drive, &regs);
 182     }
 183     c += probe_bda_drive(drive);
 184     dskprobe_pause(&regs);
 185     return c;
 186 }
 187
 188 /*
 189  * We will probe a contiguous range of BIOS drive, starting with drive
 190  * number 'start'.  We probe with a few different methods, and return
 191  * the first drive which doesn't respond to any of the probes.
 192  */
 193 uint8_t probe_drive_range(uint8_t start)
 194 {
 195     uint8_t drive = start;
 196     while (multi_probe_drive(drive)) {
 197         drive++;
 198         /* Check for passing the floppy/HDD boundary */
 199         if ((drive & 0x7F) == 0)
 200             break;
 201     }
 202     return drive;
 203 }
 204
 205 /* Dummy printf() that does nothing */
 206 static int no_printf(const char *ignored, ...)
 207 {
 208     (void)ignored;
 209     return 0;
 210 }
 211
 212 /* Pause if we are in debug-mode */
 213 static void dskprobe_pause(com32sys_t * regs)
 214 {
 215     if (!DBG_DSKPROBE)
 216         return;
 217     dskprobe_printf("Press a key to continue...\n");
 218     memset(regs, 0, sizeof *regs);
 219     regs->eax.w[0] = 0;
 220     intcall(0x16, regs, NULL);
 221     return;
 222 }