/*
* 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)
movb $0, (EDD_MBR_SIG_NR_BUF)
movb $0, (EDDNR)
# Check the command line for two options:
# edd=of disables EDD completely (edd=off)
# edd=sk skips the MBR test (edd=skipmbr)
pushl %esi
cmpl $0, %cs:cmd_line_ptr
jz done_cl
movl %cs:(cmd_line_ptr), %esi
# ds:esi has the pointer to the command line now
movl $(COMMAND_LINE_SIZE-7), %ecx
# loop through kernel command line one byte at a time
cl_loop:
cmpl $EDD_CL_EQUALS, (%si)
jz found_edd_equals
incl %esi
loop cl_loop
jmp done_cl
found_edd_equals:
# only looking at first two characters after equals
addl $4, %esi
cmpw $EDD_CL_OFF, (%si) # edd=of
jz do_edd_off
cmpw $EDD_CL_SKIP, (%si) # edd=sk
jz do_edd_skipmbr
jmp done_cl
do_edd_skipmbr:
popl %esi
jmp edd_start
do_edd_off:
popl %esi
jmp edd_done
done_cl:
popl %esi
# 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
