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starting write-multiple support

This commit is contained in:
Kartik K. Agaram 2021-04-17 19:45:41 -07:00
parent 1154db7a74
commit 31a2c8aac6
1 changed files with 55 additions and 52 deletions
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107
boot.subx
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@ -987,62 +987,65 @@ store-sectors: # disk: (addr disk), lba: int, n: int, in: (addr stream byte)
(ata-sector-count *(ebp+8) *(ebp+0x10))
(ata-lba *(ebp+8) *(ebp+0xc))
(ata-command *(ebp+8) 0x30) # write sectors with retries
# wait
(while-ata-busy *(ebp+8))
(until-ata-ready-for-data *(ebp+8))
# var data-port/edx = disk->data-port
8b/-> *(ebp+8) 0/r32/eax
8b/-> *(eax+0x24) 2/r32/edx
# send data
b9/copy-to-ecx 0x200/imm32 # 512 bytes per sector
# . var first-byte/ebx: byte
# . when it's more than 0xff, we're at an even-numbered byte
bb/copy-to-ebx 0xffff/imm32
$store-sectors:loop:
# for each sector
{
81 7/subop/compare %ecx 0/imm32
74/jump-if-= break/disp8
# this loop is slow, but the ATA spec also requires a small delay
(stream-empty? *(ebp+0x14)) # => eax
3d/compare-eax-and 0/imm32/false
75/jump-if-!= break/disp8
# read byte from stream
(read-byte *(ebp+0x14)) # => eax
# if we're at an odd-numbered byte, save it to first-byte
# wait
(while-ata-busy *(ebp+8))
(until-ata-ready-for-data *(ebp+8))
# var data-port/edx = disk->data-port
8b/-> *(ebp+8) 0/r32/eax
8b/-> *(eax+0x24) 2/r32/edx
# send data
b9/copy-to-ecx 0x200/imm32 # 512 bytes per sector
# . var first-byte/ebx: byte
# . when it's more than 0xff, we're at an even-numbered byte
bb/copy-to-ebx 0xffff/imm32
$store-sectors:store-sector:
{
81 7/subop/compare %ecx 0/imm32
74/jump-if-= break/disp8
# this loop is slow, but the ATA spec also requires a small delay
(stream-empty? *(ebp+0x14)) # => eax
3d/compare-eax-and 0/imm32/false
75/jump-if-!= break/disp8
# read byte from stream
(read-byte *(ebp+0x14)) # => eax
# if we're at an odd-numbered byte, save it to first-byte
81 7/subop/compare %ebx 0xff/imm32
{
7e/jump-if-<= break/disp8
89/<- %ebx 0/r32/eax
eb/jump $store-sectors:store-sector/disp8
}
# otherwise OR it with first-byte and write it out
c1/shift 4/subop/left %eax 8/imm8
09/or %eax 3/r32/ebx
66 ef/write-ax-into-port-dx
49/decrement-ecx
49/decrement-ecx
# reset first-byte
bb/copy-to-ebx 0xffff/imm32
eb/jump loop/disp8
}
# write out final first-byte if necessary
81 7/subop/compare %ebx 0xff/imm32
{
7e/jump-if-<= break/disp8
89/<- %ebx 0/r32/eax
eb/jump $store-sectors:loop/disp8
7f/jump-if-> break/disp8
89/<- %eax 3/r32/ebx
66 ef/write-ax-into-port-dx
49/decrement-ecx
49/decrement-ecx
}
# pad zeroes
31/xor %eax 0/r32/eax
{
81 7/subop/compare %ecx 0/imm32
74/jump-if-= break/disp8
66 ef/write-ax-into-port-dx
49/decrement-ecx
49/decrement-ecx
eb/jump loop/disp8
}
# otherwise OR it with first-byte and write it out
c1/shift 4/subop/left %eax 8/imm8
09/or %eax 3/r32/ebx
66 ef/write-ax-into-port-dx
49/decrement-ecx
49/decrement-ecx
# reset first-byte
bb/copy-to-ebx 0xffff/imm32
eb/jump loop/disp8
}
# write out first-byte if necessary
81 7/subop/compare %ebx 0xff/imm32
{
7f/jump-if-> break/disp8
89/<- %eax 3/r32/ebx
66 ef/write-ax-into-port-dx
49/decrement-ecx
49/decrement-ecx
}
# pad zeroes
31/xor %eax 0/r32/eax
{
81 7/subop/compare %ecx 0/imm32
74/jump-if-= break/disp8
66 ef/write-ax-into-port-dx
49/decrement-ecx
49/decrement-ecx
eb/jump loop/disp8
}
$store-sectors:end:
# . restore registers