[Qemu-devel] Fix for bochs vbe issues

[Matthew Mastracci]

I found a way to fix the bochs VBE issues in Windows 2000.  It looks 
really good in 16+ bit color.  The changes in this patch are:

- Use linear (chain-4) mode for all VBE_DISPI_ENABLED modes
- Add ff80 and ff81 as valid ioport registers (these are the old ports, 
still used by the driver)

Some of the issues with the patch:

- There are black lines that appear on the screen at what appear to be 
lines that span a display bank.  This only seems to happen in 8- or 
24-bit.  Puzzling!
- The shutdown screen in windows 2000 is corrupted.

A better patch might tweak some of the sequence controller and bank 
select registers to set the chain-4 mode, but I haven't tried that yet.

diff -u -r ./hw/vga.c ../../qemu-0.5.4/hw/vga.c
--- ./hw/vga.c  2004-04-26 15:17:28.000000000 -0600
+++ ../../qemu-0.5.4/hw/vga.c   2004-04-27 21:46:20.828796000 -0600
@@ -678,7 +678,10 @@
        break;
    }

-    if (s->sr[4] & 0x08) {
+       if (s->vbe_regs[VBE_DISPI_INDEX_ENABLE] & VBE_DISPI_ENABLED) {
+        /* VBE mode : simplest access */
+        ret = s->vram_ptr[addr];
+       } else if (s->sr[4] & 0x08) {
        /* chain 4 mode : simplest access */
        ret = s->vram_ptr[addr];
    } else if (s->gr[5] & 0x10) {
@@ -756,7 +759,17 @@
        break;
    }

-    if (s->sr[4] & 0x08) {
+       if (s->vbe_regs[VBE_DISPI_INDEX_ENABLE] & VBE_DISPI_ENABLED) {
+        /* VBE mode : simplest access */
+        plane = (s->gr[4] & 2) | (addr & 1);
+        if (s->sr[2] & (1 << plane)) {
+            s->vram_ptr[addr] = val;
+#ifdef DEBUG_VGA_MEM
+            printf("vga: VBE: [0x%x]\n", addr);
+#endif
+            cpu_physical_memory_set_dirty(s->vram_offset + addr);
+        }
+       } else if (s->sr[4] & 0x08) {
        /* chain 4 mode : simplest access */
        plane = addr & 3;
        if (s->sr[2] & (1 << plane)) {
@@ -1768,6 +1781,11 @@

    register_ioport_write(0x1ce, 1, 2, vbe_ioport_write, s);
    register_ioport_write(0x1cf, 1, 2, vbe_ioport_write, s);
+    register_ioport_read(0xff80, 1, 2, vbe_ioport_read, s);
+    register_ioport_read(0xff81, 1, 2, vbe_ioport_read, s);
+
+    register_ioport_write(0xff80, 1, 2, vbe_ioport_write, s);
+    register_ioport_write(0xff81, 1, 2, vbe_ioport_write, s);
#endif

    vga_io_memory = cpu_register_io_memory(0, vga_mem_read, vga_mem_write);

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