diff options
| author | Paolo Bonzini <pbonzini@redhat.com> | 2014-12-29 14:43:42 +0100 |
|---|---|---|
| committer | Paolo Bonzini <pbonzini@redhat.com> | 2024-01-18 10:43:13 +0100 |
| commit | 9b53b95a1c3b46e5a54734a46f37790460c9265e (patch) | |
| tree | 9edfc2fa6e3c0434ac065edae3bc6c56786dffff /hw/display | |
| parent | f9b925fd41337027e959baeb23d714b5214cd5ff (diff) | |
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>
Diffstat (limited to 'hw/display')
| -rw-r--r-- | hw/display/vga-helpers.h | 9 | ||||
| -rw-r--r-- | hw/display/vga.c | 3 |
2 files changed, 8 insertions, 4 deletions
diff --git a/hw/display/vga-helpers.h b/hw/display/vga-helpers.h index 10e9cfd40a..83b9a15604 100644 --- a/hw/display/vga-helpers.h +++ b/hw/display/vga-helpers.h @@ -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)]); diff --git a/hw/display/vga.c b/hw/display/vga.c index fea26f9123..5bf4d14f34 100644 --- a/hw/display/vga.c +++ b/hw/display/vga.c @@ -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) * |