fbdev: make FB_BACKLIGHT a tristate

BACKLIGHT_CLASS_DEVICE is already tristate, but a dependency
FB_BACKLIGHT prevents it from being built as a module.  There
doesn't seem to be any particularly good reason for this, so
switch FB_BACKLIGHT over to tristate.
Signed-off-by: Rob Clark <robdclark@gmail.com>
Tested-by: Arnd Bergmann <arnd@arndb.de>
Cc: Simon Horman <horms+renesas@verge.net.au>
Cc: Geert Uytterhoeven <geert+renesas@glider.be>
Cc: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: Ulf Magnusson <ulfalizer@gmail.com>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Hans de Goede <j.w.r.degoede@gmail.com>
Signed-off-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>

drivers/video/fbdev/Kconfig

@@ -184,7 +184,7 @@ config FB_MACMODES
        depends on FB
 
 config FB_BACKLIGHT
-	bool
+	tristate
 	depends on FB
 	select BACKLIGHT_LCD_SUPPORT
 	select BACKLIGHT_CLASS_DEVICE

drivers/video/fbdev/core/fbsysfs.c

@@ -60,7 +60,7 @@ struct fb_info *framebuffer_alloc(size_t size, struct device *dev)
 	info->device = dev;
 	info->fbcon_rotate_hint = -1;
 
-#ifdef CONFIG_FB_BACKLIGHT
+#if IS_ENABLED(CONFIG_FB_BACKLIGHT)
 	mutex_init(&info->bl_curve_mutex);
 #endif
 
@@ -429,7 +429,7 @@ static ssize_t show_fbstate(struct device *device,
 	return snprintf(buf, PAGE_SIZE, "%d\n", fb_info->state);
 }
 
-#ifdef CONFIG_FB_BACKLIGHT
+#if IS_ENABLED(CONFIG_FB_BACKLIGHT)
 static ssize_t store_bl_curve(struct device *device,
 			      struct device_attribute *attr,
 			      const char *buf, size_t count)
@@ -510,7 +510,7 @@ static struct device_attribute device_attrs[] = {
 	__ATTR(stride, S_IRUGO, show_stride, NULL),
 	__ATTR(rotate, S_IRUGO|S_IWUSR, show_rotate, store_rotate),
 	__ATTR(state, S_IRUGO|S_IWUSR, show_fbstate, store_fbstate),
-#ifdef CONFIG_FB_BACKLIGHT
+#if IS_ENABLED(CONFIG_FB_BACKLIGHT)
 	__ATTR(bl_curve, S_IRUGO|S_IWUSR, show_bl_curve, store_bl_curve),
 #endif
 };
@@ -551,7 +551,7 @@ void fb_cleanup_device(struct fb_info *fb_info)
 	}
 }
 
-#ifdef CONFIG_FB_BACKLIGHT
+#if IS_ENABLED(CONFIG_FB_BACKLIGHT)
 /* This function generates a linear backlight curve
  *
  *     0: off

include/linux/fb.h

@@ -485,7 +485,7 @@ struct fb_info {
 	struct list_head modelist;      /* mode list */
 	struct fb_videomode *mode;	/* current mode */
 
-#ifdef CONFIG_FB_BACKLIGHT
+#if IS_ENABLED(CONFIG_FB_BACKLIGHT)
 	/* assigned backlight device */
 	/* set before framebuffer registration, 
 	   remove after unregister */

include/uapi/linux/fb.h

@@ -393,11 +393,9 @@ struct fb_cursor {
 	struct fb_image	image;	/* Cursor image */
 };
 
-#ifdef CONFIG_FB_BACKLIGHT
 /* Settings for the generic backlight code */
 #define FB_BACKLIGHT_LEVELS	128
 #define FB_BACKLIGHT_MAX	0xFF
-#endif
 
 
 #endif /* _UAPI_LINUX_FB_H */