vgabios: Simplify planar4 vgafb code.

Don't bother programming the vga registers to manipulate the
framebuffer when in planar4 mode.  Instead, just switch between the
four planes and do the manipulation with regular reads and writes.
This makes the code simpler to understand (the vga hardware
manipulations are arcane and complex).

Note, this could make text scrolling in planar4 mode slower and more
likely to result in tearing.  However, it's unlikely anything
important uses the vgabios in planar4 mode.

Signed-off-by: Kevin O'Connor <kevin@koconnor.net>

1 files changed, 44 insertions, 49 deletions

diff --git a/vgasrc/vgafb.c b/vgasrc/vgafb.c
index b6daba6..71a5719 100644
--- a/vgasrc/vgafb.c
+++ b/vgasrc/vgafb.c
@@ -8,7 +8,7 @@
 #include "biosvar.h" // GET_BDA
 #include "util.h" // memset_far
 #include "vgahw.h" // vgahw_find_mode
-#include "stdvga.h" // stdvga_grdc_write
+#include "stdvga.h" // stdvga_planar4_plane
 
 
 /****************************************************************
@@ -55,19 +55,22 @@ scroll_pl4(struct vgamode_s *vmode_g, int nblines, int attr
         src_far = dest_far - nblines * cheight * stride;
         stride = -stride;
     }
+    if (attr < 0)
+        attr = 0;
     int cols = lr.x - ul.x + 1;
     int rows = lr.y - ul.y + 1;
-    if (nblines < rows) {
-        stdvga_grdc_write(0x05, 0x01);
-        dest_far = memcpy_stride(SEG_GRAPH, dest_far, src_far, cols * cwidth
+    int i;
+    for (i=0; i<4; i++) {
+        stdvga_planar4_plane(i);
+        void *dest = dest_far;
+        if (nblines < rows)
+            dest = memcpy_stride(SEG_GRAPH, dest, src_far, cols * cwidth
                                  , stride, (rows - nblines) * cheight);
+        u8 pixels = (attr & (1<<i)) ? 0xff : 0x00;
+        memset_stride(SEG_GRAPH, dest, pixels, cols * cwidth
+                      , stride, nblines * cheight);
     }
-    if (attr < 0)
-        attr = 0;
-    stdvga_grdc_write(0x05, 0x02);
-    memset_stride(SEG_GRAPH, dest_far, attr, cols * cwidth
-                  , stride, nblines * cheight);
-    stdvga_grdc_write(0x05, 0x00);
+    stdvga_planar4_plane(-1);
 }
 
 static void
@@ -88,6 +91,8 @@ scroll_cga(struct vgamode_s *vmode_g, int nblines, int attr
         src_far = dest_far - nblines * cheight * stride;
         stride = -stride;
     }
+    if (attr < 0)
+        attr = 0;
     int cols = lr.x - ul.x + 1;
     int rows = lr.y - ul.y + 1;
     if (nblines < rows) {
@@ -96,8 +101,6 @@ scroll_cga(struct vgamode_s *vmode_g, int nblines, int attr
         dest_far = memcpy_stride(SEG_CTEXT, dest_far, src_far, cols * cwidth
                                  , stride, (rows - nblines) * cheight);
     }
-    if (attr < 0)
-        attr = 0;
     memset_stride(SEG_CTEXT, dest_far + 0x2000, attr, cols * cwidth
                   , stride, nblines * cheight);
     memset_stride(SEG_CTEXT, dest_far, attr, cols * cwidth
@@ -122,13 +125,13 @@ scroll_lin(struct vgamode_s *vmode_g, int nblines, int attr
         src_far = dest_far - nblines * cheight * stride;
         stride = -stride;
     }
+    if (attr < 0)
+        attr = 0;
     int cols = lr.x - ul.x + 1;
     int rows = lr.y - ul.y + 1;
     if (nblines < rows)
         dest_far = memcpy_stride(SEG_GRAPH, dest_far, src_far, cols * cwidth
                                  , stride, (rows - nblines) * cheight);
-    if (attr < 0)
-        attr = 0;
     memset_stride(SEG_GRAPH, dest_far, attr, cols * cwidth
                   , stride, nblines * cheight);
 }
@@ -151,15 +154,15 @@ scroll_text(struct vgamode_s *vmode_g, int nblines, int attr
         src_far = dest_far - nblines * cheight * stride;
         stride = -stride;
     }
+    if (attr < 0)
+        attr = 0x07;
+    attr = (attr << 8) | ' ';
     int cols = lr.x - ul.x + 1;
     int rows = lr.y - ul.y + 1;
     u16 seg = GET_GLOBAL(vmode_g->sstart);
     if (nblines < rows)
         dest_far = memcpy_stride(seg, dest_far, src_far, cols * cwidth
                                  , stride, (rows - nblines) * cheight);
-    if (attr < 0)
-        attr = 0x07;
-    attr = (attr << 8) | ' ';
     memset16_stride(seg, dest_far, attr, cols * cwidth
                     , stride, nblines * cheight);
 }
@@ -217,29 +220,20 @@ write_gfx_char_pl4(struct vgamode_s *vmode_g
     }
     u16 addr = cp.x + cp.y * cheight * nbcols;
     u16 src = ca.car * cheight;
-    stdvga_sequ_write(0x02, 0x0f);
-    stdvga_grdc_write(0x05, 0x02);
-    if (ca.attr & 0x80)
-        stdvga_grdc_write(0x03, 0x18);
-    else
-        stdvga_grdc_write(0x03, 0x00);
-    u8 i;
-    for (i = 0; i < cheight; i++) {
-        u8 *dest_far = (void*)(addr + i * nbcols);
-        u8 j;
-        for (j = 0; j < 8; j++) {
-            u8 mask = 0x80 >> j;
-            stdvga_grdc_write(0x08, mask);
-            GET_FARVAR(SEG_GRAPH, *(volatile u8*)dest_far);
-            if (GET_GLOBAL(fdata_g[src + i]) & mask)
-                SET_FARVAR(SEG_GRAPH, *dest_far, ca.attr & 0x0f);
-            else
-                SET_FARVAR(SEG_GRAPH, *dest_far, 0x00);
+    int i;
+    for (i=0; i<4; i++) {
+        stdvga_planar4_plane(i);
+        u8 colors = ((ca.attr & (1<<i)) ? 0xff : 0x00);
+        int j;
+        for (j = 0; j < cheight; j++) {
+            u8 *dest_far = (void*)(addr + j * nbcols);
+            u8 pixels = colors & GET_GLOBAL(fdata_g[src + j]);
+            if (ca.attr & 0x80)
+                pixels ^= GET_FARVAR(SEG_GRAPH, *dest_far);
+            SET_FARVAR(SEG_GRAPH, *dest_far, pixels);
         }
     }
-    stdvga_grdc_write(0x08, 0xff);
-    stdvga_grdc_write(0x05, 0x00);
-    stdvga_grdc_write(0x03, 0x00);
+    stdvga_planar4_plane(-1);
 }
 
 static void
@@ -407,20 +401,20 @@ vgafb_write_pixel(u8 color, u16 x, u16 y)
     if (!vmode_g)
         return;
 
-    u8 *addr_far, mask, attr, data;
+    u8 *addr_far, mask, attr, data, i;
     switch (GET_GLOBAL(vmode_g->memmodel)) {
     case MM_PLANAR:
         addr_far = (void*)(x / 8 + y * GET_BDA(video_cols));
         mask = 0x80 >> (x & 0x07);
-        stdvga_grdc_write(0x08, mask);
-        stdvga_grdc_write(0x05, 0x02);
-        GET_FARVAR(SEG_GRAPH, *(volatile u8*)addr_far);
-        if (color & 0x80)
-            stdvga_grdc_write(0x03, 0x18);
-        SET_FARVAR(SEG_GRAPH, *addr_far, color);
-        stdvga_grdc_write(0x08, 0xff);
-        stdvga_grdc_write(0x05, 0x00);
-        stdvga_grdc_write(0x03, 0x00);
+        for (i=0; i<4; i++) {
+            stdvga_planar4_plane(i);
+            u8 colors = (color & (1<<i)) ? 0xff : 0x00;
+            u8 orig = GET_FARVAR(SEG_GRAPH, *addr_far);
+            if (color & 0x80)
+                colors ^= orig;
+            SET_FARVAR(SEG_GRAPH, *addr_far, (colors & mask) | (orig & ~mask));
+        }
+        stdvga_planar4_plane(-1);
         break;
     case MM_CGA:
         if (GET_GLOBAL(vmode_g->depth) == 2)
@@ -470,11 +464,12 @@ vgafb_read_pixel(u16 x, u16 y)
         mask = 0x80 >> (x & 0x07);
         attr = 0x00;
         for (i = 0; i < 4; i++) {
-            stdvga_grdc_write(0x04, i);
+            stdvga_planar4_plane(i);
             data = GET_FARVAR(SEG_GRAPH, *addr_far) & mask;
             if (data > 0)
                 attr |= (0x01 << i);
         }
+        stdvga_planar4_plane(-1);
         break;
     case MM_CGA:
         addr_far = (void*)((x >> 2) + (y >> 1) * 80);