fbdev: stifb: Provide valid pixelclock and add fb_check_var() checks

Find a valid modeline depending on the machine graphic card
configuration and add the fb_check_var() function to validate
Xorg provided graphics settings.
Signed-off-by: Helge Deller <deller@gmx.de>
Cc: stable@vger.kernel.org

drivers/video/fbdev/stifb.c

@@ -921,6 +921,28 @@ SETUP_HCRX(struct stifb_info *fb)
 
 /* ------------------- driver specific functions --------------------------- */
 
+static int
+stifb_check_var(struct fb_var_screeninfo *var, struct fb_info *info)
+{
+	struct stifb_info *fb = container_of(info, struct stifb_info, info);
+
+	if (var->xres != fb->info.var.xres ||
+	    var->yres != fb->info.var.yres ||
+	    var->bits_per_pixel != fb->info.var.bits_per_pixel)
+		return -EINVAL;
+
+	var->xres_virtual = var->xres;
+	var->yres_virtual = var->yres;
+	var->xoffset = 0;
+	var->yoffset = 0;
+	var->grayscale = fb->info.var.grayscale;
+	var->red.length = fb->info.var.red.length;
+	var->green.length = fb->info.var.green.length;
+	var->blue.length = fb->info.var.blue.length;
+
+	return 0;
+}
+
 static int
 stifb_setcolreg(u_int regno, u_int red, u_int green,
 	      u_int blue, u_int transp, struct fb_info *info)
@@ -1145,6 +1167,7 @@ stifb_init_display(struct stifb_info *fb)
 
 static const struct fb_ops stifb_ops = {
 	.owner		= THIS_MODULE,
+	.fb_check_var	= stifb_check_var,
 	.fb_setcolreg	= stifb_setcolreg,
 	.fb_blank	= stifb_blank,
 	.fb_fillrect	= stifb_fillrect,
@@ -1164,6 +1187,7 @@ static int __init stifb_init_fb(struct sti_struct *sti, int bpp_pref)
 	struct stifb_info *fb;
 	struct fb_info *info;
 	unsigned long sti_rom_address;
+	char modestr[32];
 	char *dev_name;
 	int bpp, xres, yres;
 
@@ -1342,6 +1366,9 @@ static int __init stifb_init_fb(struct sti_struct *sti, int bpp_pref)
 	info->flags = FBINFO_HWACCEL_COPYAREA | FBINFO_HWACCEL_FILLRECT;
 	info->pseudo_palette = &fb->pseudo_palette;
 
+	scnprintf(modestr, sizeof(modestr), "%dx%d-%d", xres, yres, bpp);
+	fb_find_mode(&info->var, info, modestr, NULL, 0, NULL, bpp);
+
 	/* This has to be done !!! */
 	if (fb_alloc_cmap(&info->cmap, NR_PALETTE, 0))
 		goto out_err1;