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.section .text
.globl init_graphics
init_graphics:
push {lr}
@ set Video Controller resolution to 640x480x16bit
@ 16-bit, cause the 8-bit depth needs a palette
ldr r1, =vc_set_res
bl mb0_c8_write
bl mb0_c8_read
tst r0, #0x80000000
beq .vc_init_fail
@ get VC framebuffer address
ldr r1, =vc_alloc_fb
bl mb0_c8_write
bl mb0_c8_read
tst r0, #0x80000008
beq .vc_init_fail
@ check if the address is correct
ldr r0, [r1, #20]
cmp r0, #0
beq .vc_init_fail
@ draw "NO OS" text
@bl vc_draw_no_os_bmp
ldr r1, =vram_base
str r0, [r1]
pop {pc}
.vc_init_fail:
ldr r1, =txt_vc_fail
bl uart_string
pop {pc}
.globl draw_pix
draw_pix:
push {r0, r1, r2, r3, r4, lr}
ldr r4, =vram_base
ldr r4, [r4]
mov r3, #2
mul r0, r3
add r4, r0
push {r2}
mov r2, #640
mul r2, r3
mul r3, r1, r2
add r4, r3
pop {r1}
str r1, [r4]
pop {r0, r1, r2, r3, r4, pc}
@@@@@@@@@@@@@@@ VC @@@@@@@@@@@@@@
.equ MBOX0, 0x3f00b880
@ writes to mailbox #0, channel 8
@ r1 - message
mb0_c8_write:
message .req r1
mailbox .req r3
status .req r2
ldr mailbox, =MBOX0
.mb0_full:
ldr status, [mailbox, #0x18]
tst status, #0x80000000 @ mailbox full flag
bne .mb0_full
add message, #8 @ channel 8
str message, [mailbox, #0x20] @ write addr
sub message, #8
.unreq mailbox
.unreq message
.unreq status
mov pc, lr
@ reads from mailbox #0, channel 8
@ r1 - message
@ returns status in r0
mb0_c8_read:
message .req r1
mailbox .req r2
status .req r3
value .req r4
ldr mailbox, =MBOX0
.mb0_empty:
ldr status, [mailbox, #0x18]
tst status, #0x40000000 @ mailbox empty flag
bne .mb0_empty
ldr value, [mailbox] @ check if the message channel is 8
and r0, value, #0xf
teq r0, #8
bne .mb0_empty
ldr r0, [message, #4]
.unreq message
.unreq mailbox
.unreq status
.unreq value
mov pc, lr
@ raspi mailbox requests, must be padded to 16 bytes
.align 4
vc_set_res: .word 80, 0 @ total size, code (0=req)
.word 0x00048003, 8, 8, 640, 480 @ set physical size (640x480)
.word 0x00048004, 8, 8, 640, 480 @ set virtual size (640x480)
.word 0x00048005, 4, 4, 16 @ set depth (16-bit)
.word 0, 0, 0, 0 @ end tag & padding
vc_alloc_fb: .word 32, 0 @ total size, code (0=req)
.word 0x00040001, 8, 4, 16, 0 @ allocate framebuffer
.word 0 @ end tag & padding
.align 2
txt_welcome: .asciz "No OS installed\r\n"
txt_vc_fail: .asciz "VC initialization failed\r\n"
.align 2
.globl vram_base
vram_base: .word 0,0
vmem: .word 0xFFFF
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