[PATCH] vgacon: no vertical resizing on EGA

EGA boards suck: they mostly have write-only registers.  This is
particularly problematic for the overflow register: for being able to write
to it, we would have to handle vertical sync & such too, which (I'd say)
would potentially break a lot of configurations.  Instead, just disabling
vertical resize for EGA boards is just nice enough (horizontal resize still
works).

Fixes http://bugzilla.kernel.org/show_bug.cgi?id=6106

Signed-off-by: Samuel Thibault <[email protected]>
Cc: Rafal Olearski <[email protected]>
Cc: "Antonino A. Daplas" <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

drivers/video/console/vgacon.c

@@ -509,57 +509,60 @@ static int vgacon_doresize(struct vc_data *c,
 {
 	unsigned long flags;
 	unsigned int scanlines = height * c->vc_font.height;
-	u8 scanlines_lo, r7, vsync_end, mode, max_scan;
+	u8 scanlines_lo = 0, r7 = 0, vsync_end = 0, mode, max_scan;
 
 	spin_lock_irqsave(&vga_lock, flags);
 
-	outb_p(VGA_CRTC_MAX_SCAN, vga_video_port_reg);
-	max_scan = inb_p(vga_video_port_val);
-
-	if (max_scan & 0x80)
-		scanlines <<= 1;
-
 	vgacon_xres = width * VGA_FONTWIDTH;
 	vgacon_yres = height * c->vc_font.height;
-	outb_p(VGA_CRTC_MODE, vga_video_port_reg);
-	mode = inb_p(vga_video_port_val);
+	if (vga_video_type >= VIDEO_TYPE_VGAC) {
+		outb_p(VGA_CRTC_MAX_SCAN, vga_video_port_reg);
+		max_scan = inb_p(vga_video_port_val);
 
-	if (mode & 0x04)
-		scanlines >>= 1;
+		if (max_scan & 0x80)
+			scanlines <<= 1;
 
-	scanlines -= 1;
-	scanlines_lo = scanlines & 0xff;
+		outb_p(VGA_CRTC_MODE, vga_video_port_reg);
+		mode = inb_p(vga_video_port_val);
 
-	outb_p(VGA_CRTC_OVERFLOW, vga_video_port_reg);
-	r7 = inb_p(vga_video_port_val) & ~0x42;
+		if (mode & 0x04)
+			scanlines >>= 1;
 
-	if (scanlines & 0x100)
-		r7 |= 0x02;
-	if (scanlines & 0x200)
-		r7 |= 0x40;
+		scanlines -= 1;
+		scanlines_lo = scanlines & 0xff;
 
-	/* deprotect registers */
-	outb_p(VGA_CRTC_V_SYNC_END, vga_video_port_reg);
-	vsync_end = inb_p(vga_video_port_val);
-	outb_p(VGA_CRTC_V_SYNC_END, vga_video_port_reg);
-	outb_p(vsync_end & ~0x80, vga_video_port_val);
+		outb_p(VGA_CRTC_OVERFLOW, vga_video_port_reg);
+		r7 = inb_p(vga_video_port_val) & ~0x42;
+
+		if (scanlines & 0x100)
+			r7 |= 0x02;
+		if (scanlines & 0x200)
+			r7 |= 0x40;
+
+		/* deprotect registers */
+		outb_p(VGA_CRTC_V_SYNC_END, vga_video_port_reg);
+		vsync_end = inb_p(vga_video_port_val);
+		outb_p(VGA_CRTC_V_SYNC_END, vga_video_port_reg);
+		outb_p(vsync_end & ~0x80, vga_video_port_val);
+	}
 
 	outb_p(VGA_CRTC_H_DISP, vga_video_port_reg);
 	outb_p(width - 1, vga_video_port_val);
 	outb_p(VGA_CRTC_OFFSET, vga_video_port_reg);
 	outb_p(width >> 1, vga_video_port_val);
 
-	outb_p(VGA_CRTC_V_DISP_END, vga_video_port_reg);
-	outb_p(scanlines_lo, vga_video_port_val);
-	outb_p(VGA_CRTC_OVERFLOW, vga_video_port_reg);
-	outb_p(r7,vga_video_port_val);
+	if (vga_video_type >= VIDEO_TYPE_VGAC) {
+		outb_p(VGA_CRTC_V_DISP_END, vga_video_port_reg);
+		outb_p(scanlines_lo, vga_video_port_val);
+		outb_p(VGA_CRTC_OVERFLOW, vga_video_port_reg);
+		outb_p(r7,vga_video_port_val);
 
-	/* reprotect registers */
-	outb_p(VGA_CRTC_V_SYNC_END, vga_video_port_reg);
-	outb_p(vsync_end, vga_video_port_val);
+		/* reprotect registers */
+		outb_p(VGA_CRTC_V_SYNC_END, vga_video_port_reg);
+		outb_p(vsync_end, vga_video_port_val);
+	}
 
 	spin_unlock_irqrestore(&vga_lock, flags);
-
 	return 0;
 }