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vga: mask addresses in non-VESA modes to 256k 

This allows setting the start address to a high value, and reading the
bottom of the screen from the beginning of VRAM.  Commander Keen 4
("Goodbye, Galaxy!") relies on this behavior.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Paolo Bonzini 2014-12-29 14:43:42 +01:00
parent f9b925fd41
commit 9b53b95a1c
2 changed files with 8 additions and 4 deletions
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9
hw/display/vga-helpers.h
View File

@ -108,7 +108,7 @@ static void vga_draw_line2(VGACommonState *vga, uint8_t *d,
plane_mask = mask16[vga->ar[VGA_ATC_PLANE_ENABLE] & 0xf];
width >>= 3;
for(x = 0; x < width; x++) {
data = vga_read_dword_le(vga, addr);
data = vga_read_dword_le(vga, addr & (VGA_VRAM_SIZE - 1));
data &= plane_mask;
v = expand2[GET_PLANE(data, 0)];
v |= expand2[GET_PLANE(data, 2)] << 2;
@ -144,7 +144,7 @@ static void vga_draw_line2d2(VGACommonState *vga, uint8_t *d,
plane_mask = mask16[vga->ar[VGA_ATC_PLANE_ENABLE] & 0xf];
width >>= 3;
for(x = 0; x < width; x++) {
data = vga_read_dword_le(vga, addr);
data = vga_read_dword_le(vga, addr & (VGA_VRAM_SIZE - 1));
data &= plane_mask;
v = expand2[GET_PLANE(data, 0)];
v |= expand2[GET_PLANE(data, 2)] << 2;
@ -177,7 +177,7 @@ static void vga_draw_line4(VGACommonState *vga, uint8_t *d,
plane_mask = mask16[vga->ar[VGA_ATC_PLANE_ENABLE] & 0xf];
width >>= 3;
for(x = 0; x < width; x++) {
data = vga_read_dword_le(vga, addr);
data = vga_read_dword_le(vga, addr & (VGA_VRAM_SIZE - 1));
data &= plane_mask;
v = expand4[GET_PLANE(data, 0)];
v |= expand4[GET_PLANE(data, 1)] << 1;
@ -209,7 +209,7 @@ static void vga_draw_line4d2(VGACommonState *vga, uint8_t *d,
plane_mask = mask16[vga->ar[VGA_ATC_PLANE_ENABLE] & 0xf];
width >>= 3;
for(x = 0; x < width; x++) {
data = vga_read_dword_le(vga, addr);
data = vga_read_dword_le(vga, addr & (VGA_VRAM_SIZE - 1));
data &= plane_mask;
v = expand4[GET_PLANE(data, 0)];
v |= expand4[GET_PLANE(data, 1)] << 1;
@ -242,6 +242,7 @@ static void vga_draw_line8d2(VGACommonState *vga, uint8_t *d,
palette = vga->last_palette;
width >>= 3;
for(x = 0; x < width; x++) {
addr &= VGA_VRAM_SIZE - 1;
PUT_PIXEL2(d, 0, palette[vga_read_byte(vga, addr + 0)]);
PUT_PIXEL2(d, 1, palette[vga_read_byte(vga, addr + 1)]);
PUT_PIXEL2(d, 2, palette[vga_read_byte(vga, addr + 2)]);

3
hw/display/vga.c
View File

@ -47,6 +47,9 @@ bool have_vga = true;
/* 16 state changes per vertical frame @60 Hz */
#define VGA_TEXT_CURSOR_PERIOD_MS (1000 * 2 * 16 / 60)
/* Address mask for non-VESA modes. */
#define VGA_VRAM_SIZE (256 * KiB)
/*
* Video Graphics Array (VGA)
*