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Diffstat (limited to 'arch/i386/boot/edd.S')
| -rw-r--r-- | arch/i386/boot/edd.S | 176 |
1 files changed, 176 insertions, 0 deletions
diff --git a/arch/i386/boot/edd.S b/arch/i386/boot/edd.S new file mode 100644 index 0000000..027d6b3 --- /dev/null +++ b/arch/i386/boot/edd.S @@ -0,0 +1,176 @@ +/* + * 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 retreival 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. + 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 |