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231 lines
7.2 KiB
231 lines
7.2 KiB
/*
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* BIOS Enhanced Disk Drive support
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* Copyright (C) 2002, 2003, 2004 Dell, Inc.
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* by Matt Domsch <Matt_Domsch@dell.com> October 2002
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* conformant to T13 Committee www.t13.org
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* projects 1572D, 1484D, 1386D, 1226DT
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* disk signature read by Matt Domsch <Matt_Domsch@dell.com>
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* and Andrew Wilks <Andrew_Wilks@dell.com> September 2003, June 2004
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* legacy CHS retrieval by Patrick J. LoPresti <patl@users.sourceforge.net>
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* March 2004
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* Command line option parsing, Matt Domsch, November 2004
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*/
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#include <linux/edd.h>
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#include <asm/setup.h>
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#if defined(CONFIG_EDD) || defined(CONFIG_EDD_MODULE)
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# It is assumed that %ds == INITSEG here
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movb $0, (EDD_MBR_SIG_NR_BUF)
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movb $0, (EDDNR)
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# Check the command line for options:
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# edd=of disables EDD completely (edd=off)
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# edd=sk skips the MBR test (edd=skipmbr)
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# edd=on re-enables EDD (edd=on)
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pushl %esi
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movw $edd_mbr_sig_start, %di # Default to edd=on
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movl %cs:(cmd_line_ptr), %esi
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andl %esi, %esi
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jz old_cl # Old boot protocol?
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# Convert to a real-mode pointer in fs:si
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movl %esi, %eax
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shrl $4, %eax
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movw %ax, %fs
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andw $0xf, %si
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jmp have_cl_pointer
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# Old-style boot protocol?
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old_cl:
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push %ds # aka INITSEG
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pop %fs
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cmpw $0xa33f, (0x20)
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jne done_cl # No command line at all?
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movw (0x22), %si # Pointer relative to INITSEG
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# fs:si has the pointer to the command line now
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have_cl_pointer:
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# Loop through kernel command line one byte at a time. Just in
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# case the loader is buggy and failed to null-terminate the command line
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# terminate if we get close enough to the end of the segment that we
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# cannot fit "edd=XX"...
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cl_atspace:
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cmpw $-5, %si # Watch for segment wraparound
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jae done_cl
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movl %fs:(%si), %eax
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andb %al, %al # End of line?
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jz done_cl
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cmpl $EDD_CL_EQUALS, %eax
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jz found_edd_equals
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cmpb $0x20, %al # <= space consider whitespace
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ja cl_skipword
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incw %si
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jmp cl_atspace
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cl_skipword:
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cmpw $-5, %si # Watch for segment wraparound
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jae done_cl
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movb %fs:(%si), %al # End of string?
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andb %al, %al
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jz done_cl
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cmpb $0x20, %al
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jbe cl_atspace
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incw %si
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jmp cl_skipword
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found_edd_equals:
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# only looking at first two characters after equals
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# late overrides early on the command line, so keep going after finding something
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movw %fs:4(%si), %ax
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cmpw $EDD_CL_OFF, %ax # edd=of
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je do_edd_off
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cmpw $EDD_CL_SKIP, %ax # edd=sk
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je do_edd_skipmbr
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cmpw $EDD_CL_ON, %ax # edd=on
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je do_edd_on
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jmp cl_skipword
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do_edd_skipmbr:
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movw $edd_start, %di
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jmp cl_skipword
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do_edd_off:
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movw $edd_done, %di
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jmp cl_skipword
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do_edd_on:
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movw $edd_mbr_sig_start, %di
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jmp cl_skipword
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done_cl:
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popl %esi
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jmpw *%di
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# Read the first sector of each BIOS disk device and store the 4-byte signature
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edd_mbr_sig_start:
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movb $0x80, %dl # from device 80
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movw $EDD_MBR_SIG_BUF, %bx # store buffer ptr in bx
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edd_mbr_sig_read:
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movl $0xFFFFFFFF, %eax
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movl %eax, (%bx) # assume failure
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pushw %bx
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movb $READ_SECTORS, %ah
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movb $1, %al # read 1 sector
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movb $0, %dh # at head 0
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movw $1, %cx # cylinder 0, sector 0
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pushw %es
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pushw %ds
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popw %es
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movw $EDDBUF, %bx # disk's data goes into EDDBUF
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pushw %dx # work around buggy BIOSes
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stc # work around buggy BIOSes
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int $0x13
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sti # work around buggy BIOSes
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popw %dx
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popw %es
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popw %bx
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jc edd_mbr_sig_done # on failure, we're done.
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cmpb $0, %ah # some BIOSes do not set CF
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jne edd_mbr_sig_done # on failure, we're done.
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movl (EDDBUF+EDD_MBR_SIG_OFFSET), %eax # read sig out of the MBR
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movl %eax, (%bx) # store success
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incb (EDD_MBR_SIG_NR_BUF) # note that we stored something
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incb %dl # increment to next device
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addw $4, %bx # increment sig buffer ptr
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cmpb $EDD_MBR_SIG_MAX, (EDD_MBR_SIG_NR_BUF) # Out of space?
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jb edd_mbr_sig_read # keep looping
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edd_mbr_sig_done:
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# Do the BIOS Enhanced Disk Drive calls
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# This consists of two calls:
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# int 13h ah=41h "Check Extensions Present"
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# int 13h ah=48h "Get Device Parameters"
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# int 13h ah=08h "Legacy Get Device Parameters"
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#
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# A buffer of size EDDMAXNR*(EDDEXTSIZE+EDDPARMSIZE) is reserved for our use
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# in the boot_params at EDDBUF. The first four bytes of which are
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# used to store the device number, interface support map and version
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# results from fn41. The next four bytes are used to store the legacy
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# cylinders, heads, and sectors from fn08. The following 74 bytes are used to
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# store the results from fn48. Starting from device 80h, fn41, then fn48
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# are called and their results stored in EDDBUF+n*(EDDEXTSIZE+EDDPARMIZE).
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# Then the pointer is incremented to store the data for the next call.
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# This repeats until either a device doesn't exist, or until EDDMAXNR
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# devices have been stored.
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# The one tricky part is that ds:si always points EDDEXTSIZE bytes into
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# the structure, and the fn41 and fn08 results are stored at offsets
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# from there. This removes the need to increment the pointer for
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# every store, and leaves it ready for the fn48 call.
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# A second one-byte buffer, EDDNR, in the boot_params stores
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# the number of BIOS devices which exist, up to EDDMAXNR.
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# In setup.c, copy_edd() stores both boot_params buffers away
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# for later use, as they would get overwritten otherwise.
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# This code is sensitive to the size of the structs in edd.h
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edd_start:
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# %ds points to the bootsector
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# result buffer for fn48
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movw $EDDBUF+EDDEXTSIZE, %si # in ds:si, fn41 results
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# kept just before that
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movb $0x80, %dl # BIOS device 0x80
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edd_check_ext:
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movb $CHECKEXTENSIONSPRESENT, %ah # Function 41
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movw $EDDMAGIC1, %bx # magic
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int $0x13 # make the call
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jc edd_done # no more BIOS devices
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cmpw $EDDMAGIC2, %bx # is magic right?
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jne edd_next # nope, next...
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movb %dl, %ds:-8(%si) # store device number
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movb %ah, %ds:-7(%si) # store version
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movw %cx, %ds:-6(%si) # store extensions
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incb (EDDNR) # note that we stored something
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edd_get_device_params:
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movw $EDDPARMSIZE, %ds:(%si) # put size
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movw $0x0, %ds:2(%si) # work around buggy BIOSes
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movb $GETDEVICEPARAMETERS, %ah # Function 48
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int $0x13 # make the call
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# Don't check for fail return
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# it doesn't matter.
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edd_get_legacy_chs:
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xorw %ax, %ax
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movw %ax, %ds:-4(%si)
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movw %ax, %ds:-2(%si)
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# Ralf Brown's Interrupt List says to set ES:DI to
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# 0000h:0000h "to guard against BIOS bugs"
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pushw %es
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movw %ax, %es
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movw %ax, %di
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pushw %dx # legacy call clobbers %dl
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movb $LEGACYGETDEVICEPARAMETERS, %ah # Function 08
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int $0x13 # make the call
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jc edd_legacy_done # failed
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movb %cl, %al # Low 6 bits are max
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andb $0x3F, %al # sector number
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movb %al, %ds:-1(%si) # Record max sect
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movb %dh, %ds:-2(%si) # Record max head number
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movb %ch, %al # Low 8 bits of max cyl
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shr $6, %cl
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movb %cl, %ah # High 2 bits of max cyl
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movw %ax, %ds:-4(%si)
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edd_legacy_done:
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popw %dx
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popw %es
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movw %si, %ax # increment si
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addw $EDDPARMSIZE+EDDEXTSIZE, %ax
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movw %ax, %si
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edd_next:
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incb %dl # increment to next device
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cmpb $EDDMAXNR, (EDDNR) # Out of space?
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jb edd_check_ext # keep looping
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edd_done:
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#endif
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