backlight: add backlight type

There may be multiple ways of controlling the backlight on a given
machine.  Allow drivers to expose the type of interface they are
providing, making it possible for userspace to make appropriate policy
decisions.

Signed-off-by: Matthew Garrett <mjg@redhat.com>
Cc: Richard Purdie <rpurdie@rpsys.net>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: David Airlie <airlied@linux.ie>
Cc: Alex Deucher <alexdeucher@gmail.com>
Cc: Ben Skeggs <bskeggs@redhat.com>
Cc: Zhang Rui <rui.zhang@intel.com>
Cc: Len Brown <lenb@kernel.org>
Cc: Jesse Barnes <jbarnes@virtuousgeek.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

drivers/video/omap2/displays/panel-taal.c

@@ -729,6 +729,8 @@ static int taal_probe(struct omap_dss_device *dssdev)
 		props.max_brightness = 255;
 	else
 		props.max_brightness = 127;
+
+	props.type = BACKLIGHT_RAW;
 	bldev = backlight_device_register("taal", &dssdev->dev, dssdev,
 					  &taal_bl_ops, &props);
 	if (IS_ERR(bldev)) {