vgabios: Refactor vga_set_mode and stdvga_set_mode.

Split out the BDA setup part of vga_set_mode to new function
modeswitch_set_bda.  Move the remaining parts (palette loading, screen
clearing, font loading) of vga_set_mode into stdvga_set_mode.

Add new mode switching flags and pass them to stdvga_set_mode, so it
does not need to inspect modeset_ctl directly.

Move code needed by stdvga_set_mode (perform_gray_scale_summing,
clear_screen) to stdvga.c.

Signed-off-by: Kevin O'Connor <kevin@koconnor.net>
diff --git a/vgasrc/bochsvga.c b/vgasrc/bochsvga.c
index 3b5c711..4ba6611 100644
--- a/vgasrc/bochsvga.c
+++ b/vgasrc/bochsvga.c
@@ -263,7 +263,7 @@
 bochsvga_set_mode(u16 mode, struct vbe_modeinfo *info)
 {
     if (info->depth == 4)
-        vga_set_mode(0x6a, 0);
+        stdvga_set_mode(0x6a, 0);
     if (info->depth == 8)
         // XXX load_dac_palette(3);
         ;
diff --git a/vgasrc/stdvga.c b/vgasrc/stdvga.c
index f40c172..b756f59 100644
--- a/vgasrc/stdvga.c
+++ b/vgasrc/stdvga.c
@@ -10,6 +10,7 @@
 #include "farptr.h" // SET_FARVAR
 #include "biosvar.h" // GET_GLOBAL
 #include "util.h" // memcpy_far
+#include "vgabios.h" // find_vga_entry
 
 // TODO
 //  * replace direct in/out calls with wrapper functions
@@ -19,14 +20,14 @@
  * Attribute control
  ****************************************************************/
 
-void
+static void
 stdvga_screen_disable(void)
 {
     inb(VGAREG_ACTL_RESET);
     outb(0x00, VGAREG_ACTL_ADDRESS);
 }
 
-void
+static void
 stdvga_screen_enable(void)
 {
     inb(VGAREG_ACTL_RESET);
@@ -265,6 +266,25 @@
     outb(GET_FARVAR(seg, info->peladdr), VGAREG_DAC_WRITE_ADDRESS);
 }
 
+void
+stdvga_perform_gray_scale_summing(u16 start, u16 count)
+{
+    stdvga_screen_disable();
+    int i;
+    for (i = start; i < start+count; i++) {
+        u8 rgb[3];
+        stdvga_get_dac_regs(GET_SEG(SS), rgb, i, 1);
+
+        // intensity = ( 0.3 * Red ) + ( 0.59 * Green ) + ( 0.11 * Blue )
+        u16 intensity = ((77 * rgb[0] + 151 * rgb[1] + 28 * rgb[2]) + 0x80) >> 8;
+        if (intensity > 0x3f)
+            intensity = 0x3f;
+
+        stdvga_set_dac_regs(GET_SEG(SS), rgb, i, 1);
+    }
+    stdvga_screen_enable();
+}
+
 
 /****************************************************************
  * Memory control
@@ -502,9 +522,53 @@
     outb(GET_FARVAR(seg, info->feature), crtc_addr - 0x4 + 0xa);
 }
 
-void
-stdvga_set_mode(struct vgamode_s *vmode_g)
+static void
+clear_screen(struct vgamode_s *vmode_g)
 {
+    switch (GET_GLOBAL(vmode_g->memmodel)) {
+    case CTEXT:
+    case MTEXT:
+        memset16_far(GET_GLOBAL(vmode_g->sstart), 0, 0x0720, 32*1024);
+        break;
+    case CGA:
+        memset16_far(GET_GLOBAL(vmode_g->sstart), 0, 0x0000, 32*1024);
+        break;
+    default:
+        // XXX - old code gets/sets/restores sequ register 2 to 0xf -
+        // but it should always be 0xf anyway.
+        memset16_far(GET_GLOBAL(vmode_g->sstart), 0, 0x0000, 64*1024);
+    }
+}
+
+void
+stdvga_set_mode(int mode, int flags)
+{
+    // find the entry in the video modes
+    struct vgamode_s *vmode_g = find_vga_entry(mode);
+    dprintf(1, "mode search %02x found %p\n", mode, vmode_g);
+    if (!vmode_g)
+        return;
+
+    // if palette loading (bit 3 of modeset ctl = 0)
+    if (!(flags & MF_NOPALETTE)) {    // Set the PEL mask
+        stdvga_set_pel_mask(GET_GLOBAL(vmode_g->pelmask));
+
+        // From which palette
+        u8 *palette_g = GET_GLOBAL(vmode_g->dac);
+        u16 palsize = GET_GLOBAL(vmode_g->dacsize) / 3;
+
+        // Always 256*3 values
+        stdvga_set_dac_regs(get_global_seg(), palette_g, 0, palsize);
+        u16 i;
+        for (i = palsize; i < 0x0100; i++) {
+            static u8 rgb[3] VAR16;
+            stdvga_set_dac_regs(get_global_seg(), rgb, i, 1);
+        }
+
+        if (flags & MF_GRAYSUM)
+            stdvga_perform_gray_scale_summing(0x00, 0x100);
+    }
+
     // Reset Attribute Ctl flip-flop
     inb(VGAREG_ACTL_RESET);
 
@@ -555,6 +619,18 @@
     // Enable video
     outb(0x20, VGAREG_ACTL_ADDRESS);
     inb(VGAREG_ACTL_RESET);
+
+    // Clear screen
+    if (!(flags & MF_NOCLEARMEM))
+        clear_screen(vmode_g);
+
+    // Write the fonts in memory
+    u8 memmodel = GET_GLOBAL(vmode_g->memmodel);
+    if (memmodel & TEXT)
+        stdvga_load_font(get_global_seg(), vgafont16, 0x100, 0, 0, 16);
+
+    // Setup BDA variables
+    modeswitch_set_bda(mode, flags, vmode_g);
 }
 
 
diff --git a/vgasrc/stdvga.h b/vgasrc/stdvga.h
index fb98304..ac5dea4 100644
--- a/vgasrc/stdvga.h
+++ b/vgasrc/stdvga.h
@@ -105,8 +105,6 @@
     u8 color_select;
 };
 
-void stdvga_screen_disable(void);
-void stdvga_screen_enable(void);
 void stdvga_set_border_color(u8 color);
 void stdvga_set_overscan_border_color(u8 color);
 u8 stdvga_get_overscan_border_color(void);
@@ -124,6 +122,7 @@
 u8 stdvga_get_pel_mask(void);
 void stdvga_save_dac_state(u16 seg, struct saveDACcolors *info);
 void stdvga_restore_dac_state(u16 seg, struct saveDACcolors *info);
+void stdvga_perform_gray_scale_summing(u16 start, u16 count);
 void stdvga_sequ_write(u8 index, u8 value);
 void stdvga_grdc_write(u8 index, u8 value);
 void stdvga_set_text_block_specifier(u8 spec);
@@ -137,7 +136,7 @@
 u16 stdvga_get_vde(void);
 void stdvga_save_state(u16 seg, struct saveVideoHardware *info);
 void stdvga_restore_state(u16 seg, struct saveVideoHardware *info);
-void stdvga_set_mode(struct vgamode_s *vmode_g);
+void stdvga_set_mode(int mode, int flags);
 void stdvga_enable_video_addressing(u8 disable);
 void stdvga_init(void);
 
diff --git a/vgasrc/vbe.c b/vgasrc/vbe.c
index f598921..df95148 100644
--- a/vgasrc/vbe.c
+++ b/vgasrc/vbe.c
@@ -12,6 +12,7 @@
 #include "util.h" // dprintf
 #include "biosvar.h" // get_global_set
 #include "bochsvga.h" // bochsvga_set_mode
+#include "stdvga.h" // stdvga_set_mode
 
 static void
 vbe_104f00(struct bregs *regs)
@@ -189,7 +190,7 @@
         dprintf(1, "set VGA mode %x\n", mode);
 
         bochsvga_hires_enable(0);
-        vga_set_mode(mode, 0);
+        stdvga_set_mode(mode, 0);
     } else { /* VBE */
         rc = bochsvga_mode_info(mode & 0x1ff, &modeinfo);
         if (rc) {
diff --git a/vgasrc/vgabios.c b/vgasrc/vgabios.c
index cb8793e..d7c559a 100644
--- a/vgasrc/vgabios.c
+++ b/vgasrc/vgabios.c
@@ -17,7 +17,7 @@
 #include "vgabios.h" // find_vga_entry
 #include "optionroms.h" // struct pci_data
 #include "config.h" // CONFIG_*
-#include "stdvga.h" // stdvga_screen_disable
+#include "stdvga.h" // stdvga_set_mode
 #include "geodelx.h" // geodelx_init
 #include "bochsvga.h" // bochsvga_init
 
@@ -47,25 +47,6 @@
  ****************************************************************/
 
 static void
-perform_gray_scale_summing(u16 start, u16 count)
-{
-    stdvga_screen_disable();
-    int i;
-    for (i = start; i < start+count; i++) {
-        u8 rgb[3];
-        stdvga_get_dac_regs(GET_SEG(SS), rgb, i, 1);
-
-        // intensity = ( 0.3 * Red ) + ( 0.59 * Green ) + ( 0.11 * Blue )
-        u16 intensity = ((77 * rgb[0] + 151 * rgb[1] + 28 * rgb[2]) + 0x80) >> 8;
-        if (intensity > 0x3f)
-            intensity = 0x3f;
-
-        stdvga_set_dac_regs(GET_SEG(SS), rgb, i, 1);
-    }
-    stdvga_screen_enable();
-}
-
-static void
 set_cursor_shape(u8 start, u8 end)
 {
     start &= 0x3f;
@@ -341,57 +322,10 @@
     SET_IVT(0x43, GET_FARVAR(seg, info->font1));
 }
 
-
-/****************************************************************
- * VGA int 10 handler
- ****************************************************************/
-
-// set video mode
+// Setup BDA after a mode switch.
 void
-vga_set_mode(u8 mode, u8 noclearmem)
+modeswitch_set_bda(int mode, int flags, struct vgamode_s *vmode_g)
 {
-    // find the entry in the video modes
-    struct vgamode_s *vmode_g = find_vga_entry(mode);
-    dprintf(1, "mode search %02x found %p\n", mode, vmode_g);
-    if (!vmode_g)
-        return;
-
-    // Read the bios mode set control
-    u8 modeset_ctl = GET_BDA(modeset_ctl);
-
-    // Then we know the number of lines
-// FIXME
-
-    // if palette loading (bit 3 of modeset ctl = 0)
-    if ((modeset_ctl & 0x08) == 0) {    // Set the PEL mask
-        stdvga_set_pel_mask(GET_GLOBAL(vmode_g->pelmask));
-
-        // From which palette
-        u8 *palette_g = GET_GLOBAL(vmode_g->dac);
-        u16 palsize = GET_GLOBAL(vmode_g->dacsize) / 3;
-
-        // Always 256*3 values
-        stdvga_set_dac_regs(get_global_seg(), palette_g, 0, palsize);
-        u16 i;
-        for (i = palsize; i < 0x0100; i++) {
-            static u8 rgb[3] VAR16;
-            stdvga_set_dac_regs(get_global_seg(), rgb, i, 1);
-        }
-
-        if ((modeset_ctl & 0x02) == 0x02)
-            perform_gray_scale_summing(0x00, 0x100);
-    }
-
-    stdvga_set_mode(vmode_g);
-
-    if (noclearmem == 0x00)
-        clear_screen(vmode_g);
-
-    // Write the fonts in memory
-    u8 memmodel = GET_GLOBAL(vmode_g->memmodel);
-    if (memmodel & TEXT)
-        stdvga_load_font(get_global_seg(), vgafont16, 0x100, 0, 0, 16);
-
     // Set the BIOS mem
     u16 cheight = GET_GLOBAL(vmode_g->cheight);
     SET_BDA(video_mode, mode);
@@ -400,10 +334,10 @@
     SET_BDA(crtc_address, stdvga_get_crtc());
     SET_BDA(video_rows, GET_GLOBAL(vmode_g->theight)-1);
     SET_BDA(char_height, cheight);
-    SET_BDA(video_ctl, (0x60 | noclearmem));
+    SET_BDA(video_ctl, 0x60 | (flags & MF_NOCLEARMEM ? 0x80 : 0x00));
     SET_BDA(video_switches, 0xF9);
     SET_BDA(modeset_ctl, GET_BDA(modeset_ctl) & 0x7f);
-    SET_BDA(cursor_type, memmodel & TEXT ? 0x0607 : 0x0000);
+    SET_BDA(cursor_type, GET_GLOBAL(vmode_g->memmodel) & TEXT ? 0x0607 : 0x0000);
     int i;
     for (i=0; i<8; i++)
         SET_BDA(cursor_pos[i], 0x0000);
@@ -435,6 +369,11 @@
     }
 }
 
+
+/****************************************************************
+ * VGA int 10 handler
+ ****************************************************************/
+
 static void
 handle_1000(struct bregs *regs)
 {
@@ -458,7 +397,11 @@
     if (bochsvga_enabled())
         bochsvga_hires_enable(0);
 
-    vga_set_mode(mode, noclearmem);
+    int flags = GET_BDA(modeset_ctl) & (MF_NOPALETTE|MF_GRAYSUM);
+    if (noclearmem)
+        flags |= MF_NOCLEARMEM;
+
+    stdvga_set_mode(mode, flags);
 }
 
 static void
@@ -731,7 +674,7 @@
 static void
 handle_10101b(struct bregs *regs)
 {
-    perform_gray_scale_summing(regs->bx, regs->cx);
+    stdvga_perform_gray_scale_summing(regs->bx, regs->cx);
 }
 
 static void
diff --git a/vgasrc/vgabios.h b/vgasrc/vgabios.h
index d31161e..0371f8c 100644
--- a/vgasrc/vgabios.h
+++ b/vgasrc/vgabios.h
@@ -26,6 +26,13 @@
     struct segoff_s font1;
 };
 
+// Mode flags
+#define MF_GRAYSUM    0x0002
+#define MF_NOPALETTE  0x0008
+#define MF_CUSTOMCRTC 0x0800
+#define MF_LINEARFB   0x4000
+#define MF_NOCLEARMEM 0x8000
+
 // vgatables.c
 struct vgamode_s;
 struct vgamode_s *find_vga_entry(u8 mode);
@@ -48,10 +55,9 @@
 struct cursorpos {
     u8 x, y, page;
 };
-void vga_set_mode(u8 mode, u8 noclearmem);
+void modeswitch_set_bda(int mode, int flags, struct vgamode_s *vmode_g);
 
 // vgafb.c
-void clear_screen(struct vgamode_s *vmode_g);
 void vgafb_scroll(int nblines, int attr
                   , struct cursorpos ul, struct cursorpos lr);
 void vgafb_write_char(struct cursorpos cp, struct carattr ca);
diff --git a/vgasrc/vgafb.c b/vgasrc/vgafb.c
index 19ab1df..38ed070 100644
--- a/vgasrc/vgafb.c
+++ b/vgasrc/vgafb.c
@@ -158,24 +158,6 @@
     }
 }
 
-void
-clear_screen(struct vgamode_s *vmode_g)
-{
-    switch (GET_GLOBAL(vmode_g->memmodel)) {
-    case CTEXT:
-    case MTEXT:
-        memset16_far(GET_GLOBAL(vmode_g->sstart), 0, 0x0720, 32*1024);
-        break;
-    case CGA:
-        memset16_far(GET_GLOBAL(vmode_g->sstart), 0, 0x0000, 32*1024);
-        break;
-    default:
-        // XXX - old code gets/sets/restores sequ register 2 to 0xf -
-        // but it should always be 0xf anyway.
-        memset16_far(GET_GLOBAL(vmode_g->sstart), 0, 0x0000, 64*1024);
-    }
-}
-
 
 /****************************************************************
  * Read/write characters to screen