fbcon: introduce for_each_registered_fb() helper

Following pattern is often used:

 for (i = 0; i < FB_MAX; i++) {
        if (registered_fb[i]) {
                ...
        }
 }

Therefore, as Andy's suggestion, for_each_registered_fb() helper can
be introduced to make the code easier to read and write by reducing
indentation level. It also saves few lines of code in each occurrence.

This patch convert all part here at the same time.
Suggested-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Yisheng Xie <ysxie@foxmail.com>
Acked-by: Hans de Goede <hdegoede@redhat.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: David Lechner <david@lechnology.com>
Signed-off-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>

drivers/video/fbdev/core/fbcon.c

@@ -2234,8 +2234,8 @@ static int fbcon_switch(struct vc_data *vc)
 	 *
 	 * info->currcon = vc->vc_num;
 	 */
-	for (i = 0; i < FB_MAX; i++) {
-		if (registered_fb[i] != NULL && registered_fb[i]->fbcon_par) {
+	for_each_registered_fb(i) {
+		if (registered_fb[i]->fbcon_par) {
 			struct fbcon_ops *o = registered_fb[i]->fbcon_par;
 
 			o->currcon = vc->vc_num;
@@ -3124,13 +3124,11 @@ static int fbcon_fb_unregistered(struct fb_info *info)
 	if (idx == info_idx) {
 		info_idx = -1;
 
-		for (i = 0; i < FB_MAX; i++) {
-			if (registered_fb[i] != NULL) {
+		for_each_registered_fb(i) {
 			info_idx = i;
 			break;
 		}
 	}
-	}
 
 	if (info_idx != -1) {
 		for (i = first_fb_vc; i <= last_fb_vc; i++) {
@@ -3609,10 +3607,8 @@ static int fbcon_output_notifier(struct notifier_block *nb,
 	deferred_takeover = false;
 	logo_shown = FBCON_LOGO_DONTSHOW;
 
-	for (i = 0; i < FB_MAX; i++) {
-		if (registered_fb[i])
+	for_each_registered_fb(i)
 		fbcon_fb_registered(registered_fb[i]);
-	}
 
 	return NOTIFY_OK;
 }
@@ -3638,12 +3634,10 @@ static void fbcon_start(void)
 
 		console_lock();
 
-		for (i = 0; i < FB_MAX; i++) {
-			if (registered_fb[i] != NULL) {
+		for_each_registered_fb(i) {
 			info_idx = i;
 			break;
 		}
-		}
 
 		do_fbcon_takeover(0);
 		console_unlock();
@@ -3669,15 +3663,12 @@ static void fbcon_exit(void)
 	kfree((void *)softback_buf);
 	softback_buf = 0UL;
 
-	for (i = 0; i < FB_MAX; i++) {
+	for_each_registered_fb(i) {
 		int pending = 0;
 
 		mapped = 0;
 		info = registered_fb[i];
 
-		if (info == NULL)
-			continue;
-
 		if (info->queue.func)
 			pending = cancel_work_sync(&info->queue);
 		DPRINTK("fbcon: %s pending work\n", (pending ? "canceled" :

drivers/video/fbdev/core/fbmem.c

@@ -1593,10 +1593,8 @@ static int do_remove_conflicting_framebuffers(struct apertures_struct *a,
 	int i, ret;
 
 	/* check all firmware fbs and kick off if the base addr overlaps */
-	for (i = 0 ; i < FB_MAX; i++) {
+	for_each_registered_fb(i) {
 		struct apertures_struct *gen_aper;
-		if (!registered_fb[i])
-			continue;
 
 		if (!(registered_fb[i]->flags & FBINFO_MISC_FIRMWARE))
 			continue;

include/linux/fb.h

@@ -650,6 +650,10 @@ extern struct fb_info *registered_fb[FB_MAX];
 extern int num_registered_fb;
 extern struct class *fb_class;
 
+#define for_each_registered_fb(i)		\
+	for (i = 0; i < FB_MAX; i++)		\
+		if (!registered_fb[i]) {} else
+
 extern int lock_fb_info(struct fb_info *info);
 
 static inline void unlock_fb_info(struct fb_info *info)