[media] rc-main: add generic scancode filtering

Add generic scancode filtering of RC input events, and fall back to
permitting any RC_FILTER_NORMAL scancode filter to be set if no s_filter
callback exists. This allows raw IR decoder events to be filtered, and
potentially allows hardware decoders to set looser filters and rely on
generic code to filter out the corner cases.

Signed-off-by: James Hogan <[e-mail]>
Reviewed-by: Antti Seppälä <[e-mail]>
Signed-off-by: Mauro Carvalho Chehab <[e-mail]>

drivers/media/rc/rc-main.c

···
 static void ir_do_keydown(struct rc_dev *dev, int scancode,
 			  u32 keycode, u8 toggle)
 {
+	struct rc_scancode_filter *filter;
 	bool new_event = !dev->keypressed ||
 			 dev->last_scancode != scancode ||
 			 dev->last_toggle != toggle;
 
 	if (new_event && dev->keypressed)
 		ir_do_keyup(dev, false);
+
+	/* Generic scancode filtering */
+	filter = &dev->scancode_filters[RC_FILTER_NORMAL];
+	if (filter->mask && ((scancode ^ filter->data) & filter->mask))
+		return;
 
 	input_event(dev->input_dev, EV_MSC, MSC_SCAN, scancode);
 
···
 		return -EINVAL;
 
 	mutex_lock(&dev->lock);
-	if (!dev->s_filter)
-		val = 0;
-	else if (fattr->mask)
+	if (fattr->mask)
 		val = dev->scancode_filters[fattr->type].mask;
 	else
 		val = dev->scancode_filters[fattr->type].data;
···
 		return ret;
 
 	/* Scancode filter not supported (but still accept 0) */
-	if (!dev->s_filter)
+	if (!dev->s_filter && fattr->type != RC_FILTER_NORMAL)
 		return val ? -EINVAL : count;
 
 	mutex_lock(&dev->lock);
···
 		local_filter.mask = val;
 	else
 		local_filter.data = val;
-	ret = dev->s_filter(dev, fattr->type, &local_filter);
-	if (ret < 0)
-		goto unlock;
+	if (dev->s_filter) {
+		ret = dev->s_filter(dev, fattr->type, &local_filter);
+		if (ret < 0)
+			goto unlock;
+	}
 
 	/* Success, commit the new filter */
 	*filter = local_filter;