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/* ----------------------------------------------------------------------- *
*
* Copyright 2009 Shao Miller - All Rights Reserved
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, Inc., 53 Temple Place Ste 330,
* Boston MA 02111-1307, USA; either version 2 of the License, or
* (at your option) any later version; incorporated herein by reference.
*
* ----------------------------------------------------------------------- */
/*
* dskprobe.c
*
* Routines for probing BIOS disk drives
*/
/*
* Uncomment for debugging
*
* #define DBG_DSKPROBE 1
*/
#include <stdint.h>
#include "memdisk.h"
#include "bda.h"
#include "conio.h"
/*
* We will probe a BIOS drive numer using INT 13h, AH=probe
* and will pass along that call's success or failure
*/
int probe_int13_ah(uint8_t drive, uint8_t probe)
{
int err;
com32sys_t regs;
memset(®s, 0, sizeof regs);
regs.eax.b[1] = probe; /* AH = probe */
regs.edx.b[0] = drive; /* DL = drive number to probe */
intcall(0x13, ®s, ®s);
err = !(regs.eflags.l & 1);
#ifdef DBG_DSKPROBE
printf("probe_int13_ah(0x%02x, 0x%02x) == %d\n", drive, probe, err);
#endif
return err;
}
/*
* We will probe the BIOS Data Area and count the drives found there.
* This heuristic then assumes that all drives of 'drive's type are
* found in a contiguous range, and returns 1 if the probed drive
* is less than or equal to the BDA count.
* This particular function's code is derived from code in setup.c by
* H. Peter Anvin. Please respect that file's copyright for this function
*/
int probe_bda_drive(uint8_t drive)
{
int bios_drives;
int err;
if (drive & 0x80) {
bios_drives = rdz_8(BIOS_HD_COUNT); /* HDD count */
} else {
uint8_t equip = rdz_8(BIOS_EQUIP);
if (equip & 1)
bios_drives = (equip >> 6) + 1; /* Floppy count */
else
bios_drives = 0;
}
err = (drive - (drive & 0x80)) >= bios_drives ? 0 : 1;
#ifdef DBG_DSKPROBE
printf("probe_bda_drive(0x%02x) == %d, count: %d\n",
drive, err, bios_drives);
#endif
return err;
}
/*
* We will probe a drive with a few different methods, returning
* the count of succesful probes
*/
int probe_drive(uint8_t drive)
{
int c = 0;
/* Only probe the BDA for floppies */
if (drive & 0x80) {
c += probe_int13_ah(drive, 0x08);
c += probe_int13_ah(drive, 0x15);
c += probe_int13_ah(drive, 0x41);
}
c += probe_bda_drive(drive);
return c;
}
/*
* We will probe a contiguous range of BIOS drive, starting with drive
* number 'start'. We probe with a few different methods, and return
* the first drive which doesn't respond to any of the probes.
*/
uint8_t probe_drive_range(uint8_t start)
{
uint8_t drive = start;
while (probe_drive(drive)) {
drive++;
/* Check for passing the floppy/HDD boundary */
if ((drive & 0x7F) == 0)
break;
}
return drive;
}
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