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Bare metal VGA: filter out non-framebuffer graphics modes

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from VESA video mode list
This commit is contained in:
tkchia 2022-09-23 10:52:45 +00:00
parent 8ed7d4df55
commit d5eb6c32f2
1 changed files with 7 additions and 7 deletions
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14
libc/vga/rlinit-vesa.S
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@ -159,17 +159,17 @@ _rlinit_vesa:
mov %al,%cl
and $0b00001011,%al # also skip if mode is unusable, or
cmp $0b00001011,%al # extra information unavailable, or
jnz .fail3 # is monochrome
jnz .fail3 # is monochrome, or is graphics w/o
mov %cl,%al # linear frame buffer
and $0b10010000,%al
cmp $0b00010000,%al
jz .fail3
call .putsp # echo mode information
call .putsp
test $0b00010000,%cl # first, echo mode attributes
setnz %al
imul $'g'-'t',%ax,%ax # - 'g': graphics; 't': text mode
add $'t',%al
shl %cl # - turn 'g' into 'G' if linear
sbb %cl,%cl # frame buffer supported
and $'G'-'g',%cl
add %cl,%al
imul $'G'-'T',%ax,%ax # - 'G': graphics; 'T': text mode
add $'T',%al
call .putc
call .putsp
xchg %ax,%si # then output