sisfb: use display information in info not in var for panning

We must not use any information in the passed var besides xoffset,
yoffset and vmode as otherwise applications might abuse it.

Fix checkpatch.pl warnings in the surrounding code.
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Cc: Aaro Koskinen <aaro.koskinen@iki.fi>
Cc: Thomas Winischhofer <thomas@winischhofer.net>
Signed-off-by: Paul Mundt <lethal@linux-sh.org>

drivers/video/sis/sis_main.c

@@ -1333,19 +1333,14 @@ sisfb_set_base_CRT2(struct sis_video_info *ivideo, unsigned int base)
 }
 
 static int
-sisfb_pan_var(struct sis_video_info *ivideo, struct fb_var_screeninfo *var)
+sisfb_pan_var(struct sis_video_info *ivideo, struct fb_info *info,
+	      struct fb_var_screeninfo *var)
 {
-	if(var->xoffset > (var->xres_virtual - var->xres)) {
-		return -EINVAL;
-	}
-	if(var->yoffset > (var->yres_virtual - var->yres)) {
-		return -EINVAL;
-	}
-
-	ivideo->current_base = (var->yoffset * var->xres_virtual) + var->xoffset;
+	ivideo->current_base = var->yoffset * info->var.xres_virtual
+			     + var->xoffset;
 
 	/* calculate base bpp dep. */
-	switch(var->bits_per_pixel) {
+	switch (info->var.bits_per_pixel) {
 	case 32:
 		break;
 	case 16:
@@ -1635,20 +1630,15 @@ sisfb_pan_display(struct fb_var_screeninfo *var, struct fb_info* info)
 	struct sis_video_info *ivideo = (struct sis_video_info *)info->par;
 	int err;
 
-	if(var->xoffset > (var->xres_virtual - var->xres))
-		return -EINVAL;
-
-	if(var->yoffset > (var->yres_virtual - var->yres))
-		return -EINVAL;
-
-	if(var->vmode & FB_VMODE_YWRAP)
+	if (var->vmode & FB_VMODE_YWRAP)
 		return -EINVAL;
 
-	if(var->xoffset + info->var.xres > info->var.xres_virtual ||
-	   var->yoffset + info->var.yres > info->var.yres_virtual)
+	if (var->xoffset + info->var.xres > info->var.xres_virtual ||
+	    var->yoffset + info->var.yres > info->var.yres_virtual)
 		return -EINVAL;
 
-	if((err = sisfb_pan_var(ivideo, var)) < 0)
+	err = sisfb_pan_var(ivideo, info, var);
+	if (err < 0)
 		return err;
 
 	info->var.xoffset = var->xoffset;