/*      $NetBSD: bios_disk.S,v 1.23 2022/09/10 12:14:17 rillig Exp $    */

/*
* Ported to boot 386BSD by Julian Elischer ([email protected]) Sept 1992
*
* Mach Operating System
* Copyright (c) 1992, 1991 Carnegie Mellon University
* All Rights Reserved.
*
* Permission to use, copy, modify and distribute this software and its
* documentation is hereby granted, provided that both the copyright
* notice and this permission notice appear in all copies of the
* software, derivative works or modified versions, and any portions
* thereof, and that both notices appear in supporting documentation.
*
* CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS"
* CONDITION.  CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND FOR
* ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE.
*
* Carnegie Mellon requests users of this software to return to
*
*  Software Distribution Coordinator  or  [email protected]
*  School of Computer Science
*  Carnegie Mellon University
*  Pittsburgh PA 15213-3890
*
* any improvements or extensions that they make and grant Carnegie Mellon
* the rights to redistribute these changes.
*/

/*
 Copyright 1988, 1989, 1990, 1991, 1992
  by Intel Corporation, Santa Clara, California.

               All Rights Reserved

Permission to use, copy, modify, and distribute this software and
its documentation for any purpose and without fee is hereby
granted, provided that the above copyright notice appears in all
copies and that both the copyright notice and this permission notice
appear in supporting documentation, and that the name of Intel
not be used in advertising or publicity pertaining to distribution
of the software without specific, written prior permission.

INTEL DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE
INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS,
IN NO EVENT SHALL INTEL BE LIABLE FOR ANY SPECIAL, INDIRECT, OR
CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
LOSS OF USE, DATA OR PROFITS, WHETHER IN ACTION OF CONTRACT,
NEGLIGENCE, OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION
WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*/

/* extracted from netbsd:sys/arch/i386/boot/bios.S */

#include <machine/asm.h>

/*
* BIOS call "INT 0x13 Function 0x0" to reset the disk subsystem
*      Call with       %ah = 0x0
*                      %dl = drive (0x80 for hard disk, 0x0 for floppy disk)
*      Return:
*                      %al = 0x0 on success; err code on failure
*/
ENTRY(biosdisk_reset)
       pusha

       movb    %al, %dl        # device

       call    _C_LABEL(prot_to_real)  # enter real mode
       .code16

       movb    $0x0, %ah       # subfunction
       int     $0x13
       setc    %bl
       movb    %ah, %bh        # save error code

       calll   _C_LABEL(real_to_prot) # back to protected mode
       .code32

       movzwl  %bx, %eax       # return value in %eax
       movl    %eax, 28(%esp)

       popa
       ret

/*
* BIOS call "INT 0x13 Function 0x2" to read sectors from disk into memory
*      Call with       %ah = 0x2
*                      %al = number of sectors
*                      %ch = cylinder
*                      %cl = sector
*                      %dh = head
*                      %dl = drive (0x80 for hard disk, 0x0 for floppy disk)
*                      %es:%bx = segment:offset of buffer
*      Return:
*                      %al = 0x0 on success; err code on failure
*
* biosdisk_read(dev, cyl, head, sect, count, buff_addr);
*
*  Note: On failure, you must reset the disk with biosdisk_reset() before
*        sending another command.
*/
ENTRY(biosdisk_read)
       pusha

       movb    44(%esp), %dh
       movw    40(%esp), %cx
       xchgb   %ch, %cl        # cylinder; the highest 2 bits of cyl is in %cl
       rorb    $2, %cl
       movb    48(%esp), %al
       orb     %al, %cl
       incb    %cl             # sector; sec starts from 1, not 0
       movb    36(%esp), %dl   # device
       movl    56(%esp), %ebx  # buffer address (may be >64k)
       movb    52(%esp), %al   # number of sectors

       call    _C_LABEL(prot_to_real)  # enter real mode
       .code16

       push    %bx
       shrl    $4, %ebx        # max segment
       mov     %ds, %si
       add     %si, %bx
       mov     %bx, %es        # %es:%bx now valid buffer address
       pop     %bx
       and     $0xf, %bx       # and min offset - to avoid overrun

       movb    $0x2, %ah       # subfunction
       int     $0x13
       setc    %al             # error code is in %ah

       calll   _C_LABEL(real_to_prot) # back to protected mode
       .code32

       andl    $0x0000FFFF, %eax  # Some bioses set high bits in %eax
                                  #  on success, interfering with our
                                  #  return value.  Clear those out.
       movl    %eax, 28(%esp)

       popa
       ret

/*
* biosdisk_getinfo(int dev):  return a word that represents the
*      max number of sectors, heads and cylinders for this device
*/
ENTRY(biosdisk_getinfo)
       push    %es
       pusha

       movb    %al, %dl                # diskinfo(drive #)

       call    _C_LABEL(prot_to_real)  # enter real mode
       .code16

       push    %dx                     # save drive #
       movb    $0x08, %ah              # ask for disk info
       int     $0x13
       pop     %bx                     # restore drive #
       jnc     ok

       testb   $0x80, %bl              # is it a hard disk?
       jnz     ok

       /*
        * Urk.  Call failed.  It is not supported for floppies by old BIOS's.
        * Guess it's a 15-sector floppy.  Initialize all the registers for
        * documentation, although we only need head and sector counts.
        */
       xorw    %ax, %ax                # set status to success
#       movb    %ah, %bh                # %bh = 0
#       movb    $2, %bl                 # %bl bits 0-3 = drive type, 2 = 1.2M
       movb    $79, %ch                # max track
       movb    $15, %cl                # max sector
       movb    $1, %dh                 # max head
#       movb    $1, %dl                 # # floppy drives installed
       # es:di = parameter table
       # carry = 0

ok:
       calll   _C_LABEL(real_to_prot)  # back to protected mode
       .code32

       /* form a longword representing all this gunk */
       shrl    $8, %eax                # clear unnecessary bits
       shll    $24, %eax
       shll    $16, %ecx               # do the same for %ecx
       shrl    $8, %ecx
       movb    %dh, %cl                # max head
       orl     %ecx, %eax              # return value in %eax
       movl    %eax, 28(%esp)

       popa
       pop     %es
       ret

/*
* int biosdisk_int13ext(int dev):
*      check for availability of int13 extensions.
*/
ENTRY(biosdisk_int13ext)
       pusha

       movb    %al, %dl                # drive #
       movw    $0x55aa, %bx

       call    _C_LABEL(prot_to_real)  # enter real mode
       .code16

       movb    $0x41, %ah              # ask for disk info
       int     $0x13
       setnc   %dl

       calll   _C_LABEL(real_to_prot)  # switch back
       .code32

       movzbl  %dl, %eax               # return value in %eax

       cmpw    $0xaa55, %bx
       sete    %dl
       andb    %dl, %al

       andb    %cl, %al
       movl    %eax, 28(%esp)

       popa
       ret

/*
* BIOS call "INT 0x13 Function 0x42" to read sectors from disk into memory
*      Call with       %ah = 0x42
*                      %ds:%si = parameter block (data buffer address
*                              must be a real mode physical address).
*                      %dl = drive (0x80 for hard disk, 0x0 for floppy disk)
*      Return:
*                      %al = 0x0 on success; err code on failure
*/
ENTRY(biosdisk_extread)
       pusha

       movl    %edx, %esi      # parameter block
       movb    %al, %dl        # device

       call    _C_LABEL(prot_to_real)  # enter real mode
       .code16

       push    %ds
       movl    %esi, %eax
       shrl    $4, %eax
       movw    %ds, %bx
       addw    %bx, %ax
       movw    %ax, %ds
       andw    $0xf, %si

       movb    $0x42, %ah      # subfunction
       int     $0x13
       setc    %bl
       movb    %ah, %bh        # save error code
       pop     %ds

       calll   _C_LABEL(real_to_prot) # back to protected mode
       .code32

       movzwl  %bx, %eax       # return value in %eax
       movl    %eax, 28(%esp)

       popa
       ret

ENTRY(biosdisk_getextinfo)
       pusha

       movl    %edx, %esi      # parameter block
       movb    %al, %dl        # device

       call    _C_LABEL(prot_to_real)  # enter real mode
       .code16

       push    %ds
       movl    %esi, %eax
       shrl    $4, %eax
       andw    $0xf, %si
       movw    %ds, %bx
       addw    %bx, %ax
       movw    %ax, %ds

       movb    $0x48, %ah      # subfunction
       int     $0x13
       setc    %bl
       pop     %ds

       calll   _C_LABEL(real_to_prot) # back to protected mode
       .code32

       movzbl  %bl, %eax       # return value in %eax
       movl    %eax, 28(%esp)

       popa
       ret

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