[PATCH v1 08/18] backlight: add backlight_is_blank()

[Sam Ravnborg]

The backlight support has two properties that express the state:
- power
- state

It is un-documented and easy to get wrong.
Add backlight_is_blank() helper to make it simpler for drivers
to get the check of the state correct.

A lot of drivers also includes checks for fb_blank.
This check is redundant when the state is checked
as thus not needed in this helper function.
Rolling out this helper to all relevant backlight drivers
will eliminate almost all accesses to fb_blank.

Signed-off-by: Sam Ravnborg <sam at ravnborg.org>
Cc: Lee Jones <lee.jones at linaro.org>
Cc: Daniel Thompson <daniel.thompson at linaro.org>
Cc: Jingoo Han <jingoohan1 at gmail.com>
---
 include/linux/backlight.h | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/include/linux/backlight.h b/include/linux/backlight.h
index b7839ea9d00a..e67e926de1e2 100644
--- a/include/linux/backlight.h
+++ b/include/linux/backlight.h
@@ -165,6 +165,23 @@ static inline int backlight_disable(struct backlight_device *bd)
 	return backlight_update_status(bd);
 }
 
+/**
+ * backlight_is_blank - Return true if display is expected to be blank
+ * @bd: the backlight device
+ *
+ * Display is expected to be blank if any of these is true::
+ *
+ *   1) if power in not UNBLANK
+ *   2) if state indicate BLANK or SUSPENDED
+ *
+ * Returns true if display is expected to be blank, false otherwise.
+ */
+static inline bool backlight_is_blank(struct backlight_device *bd)
+{
+	return bd->props.power != FB_BLANK_UNBLANK ||
+	       bd->props.state & (BL_CORE_SUSPENDED | BL_CORE_FBBLANK);
+}
+
 extern struct backlight_device *backlight_device_register(const char *name,
 	struct device *dev, void *devdata, const struct backlight_ops *ops,
 	const struct backlight_properties *props);
-- 
2.25.1