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