banan-os/bootloader/bios/framebuffer.S

157 lines
3.2 KiB
ArmAsm

.set TARGET_WIDTH, 800
.set TARGET_HEIGHT, 600
.set TARGET_BPP, 32
.code16
.section .stage2
# Find suitable video mode
# return:
# ax: video mode number if found, 0 otherwise
.global vesa_find_video_mode
vesa_find_video_mode:
pushw %ax
pushw %cx
pushw %di
pushl %esi
# clear target mode and frame buffer
movw $0, (vesa_target_mode)
movl $0, (framebuffer + 0)
movl $0, (framebuffer + 4)
movl $0, (framebuffer + 8)
movl $0, (framebuffer + 12)
movw $0, (framebuffer + 16)
# get vesa information
movw $0x4F00, %ax
movw $vesa_info_buffer, %di
int $0x10
cmpb $0x4F, %al; jne .vesa_unsupported
cmpb $0x00, %ah; jne .vesa_error
# confirm that response starts with 'VESA'
cmpl $0x41534556, (vesa_info_buffer)
jne .vesa_error
# confirm that version is atleast 2.0
cmpw $0x0200, (vesa_info_buffer + 0x04)
jb .vesa_unsupported_version
movl $(vesa_info_buffer + 0x0E), %esi
movl (%esi), %esi
.vesa_find_video_mode_loop_modes:
cmpw $0xFFFF, (%esi)
je .vesa_find_video_mode_loop_modes_done
# get info of next mode
movw $0x4F01, %ax
movw (%esi), %cx
movw $vesa_mode_info_buffer, %di
int $0x10
cmpb $0x4F, %al; jne .vesa_unsupported
cmpb $0x00, %ah; jne .vesa_error
# check whether in graphics mode
testb $0x10, (vesa_mode_info_buffer + 0)
jz .vesa_find_video_mode_next_mode
# compare mode's dimensions
cmpw $TARGET_WIDTH, (vesa_mode_info_buffer + 0x12)
jne .vesa_find_video_mode_next_mode
cmpw $TARGET_HEIGHT, (vesa_mode_info_buffer + 0x14)
jne .vesa_find_video_mode_next_mode
cmpb $TARGET_BPP, (vesa_mode_info_buffer + 0x19)
jne .vesa_find_video_mode_next_mode
movl (vesa_mode_info_buffer + 0x28), %esi
movl %esi, (framebuffer + 0)
movw (vesa_mode_info_buffer + 0x10), %ax
movw %ax, (framebuffer + 4)
movl $TARGET_WIDTH, (framebuffer + 8)
movl $TARGET_HEIGHT, (framebuffer + 12)
movb $TARGET_BPP, (framebuffer + 16)
movb $1, (framebuffer + 17)
movw %cx, (vesa_target_mode)
jmp .vesa_find_video_mode_loop_modes_done
.vesa_find_video_mode_next_mode:
addl $2, %esi
jmp .vesa_find_video_mode_loop_modes
.vesa_find_video_mode_loop_modes_done:
popl %esi
popw %di
popw %cx
popw %ax
ret
.vesa_unsupported:
movw $vesa_unsupported_msg, %si
jmp print_and_halt
.vesa_unsupported_version:
movw $vesa_unsupported_version_msg, %si
jmp print_and_halt
.vesa_error:
movw $vesa_error_msg, %si
jmp print_and_halt
# set mode found from vesa_find_video_mode. if no mode
# was found, set it to 80x25 text mode to clear the screen.
.global vesa_set_target_mode
vesa_set_target_mode:
pushw %ax
pushw %bx
movw (vesa_target_mode), %bx
testw %bx, %bx
jz .vesa_set_target_mode_generic
movw $0x4F02, %ax
orw $0x4000, %bx
int $0x10
jmp .set_video_done
.vesa_set_target_mode_generic:
movb $0x03, %al
movb $0x00, %ah
int $0x10
.set_video_done:
popw %bx
popw %ax
ret
vesa_error_msg:
.asciz "VESA error"
vesa_unsupported_msg:
.asciz "VESA unsupported"
vesa_unsupported_version_msg:
.asciz "VESA unsupported version"
vesa_success_msg:
.asciz "VESA success"
.section .bss
vesa_info_buffer:
.skip 512
vesa_mode_info_buffer:
.skip 256
vesa_target_mode:
.skip 2
.global framebuffer
framebuffer:
.skip 4 # address
.skip 4 # pitch
.skip 4 # width
.skip 4 # height
.skip 1 # bpp
.skip 1 # type