1 files changed, 33 insertions, 0 deletions
diff --git a/drivers/video/fbdev/core/fb_backlight.c b/drivers/video/fbdev/core/fb_backlight.c
new file mode 100644
index 000000000000..e2d3b3adc870
--- /dev/null
+++ b/drivers/video/fbdev/core/fb_backlight.c
@@ -0,0 +1,33 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#include <linux/export.h>
+#include <linux/fb.h>
+#include <linux/mutex.h>
+
+#if IS_ENABLED(CONFIG_FB_BACKLIGHT)
+/*
+ * This function generates a linear backlight curve
+ *
+ *     0: off
+ *   1-7: min
+ * 8-127: linear from min to max
+ */
+void fb_bl_default_curve(struct fb_info *fb_info, u8 off, u8 min, u8 max)
+{
+	unsigned int i, flat, count, range = (max - min);
+
+	mutex_lock(&fb_info->bl_curve_mutex);
+
+	fb_info->bl_curve[0] = off;
+
+	for (flat = 1; flat < (FB_BACKLIGHT_LEVELS / 16); ++flat)
+		fb_info->bl_curve[flat] = min;
+
+	count = FB_BACKLIGHT_LEVELS * 15 / 16;
+	for (i = 0; i < count; ++i)
+		fb_info->bl_curve[flat + i] = min + (range * (i + 1) / count);
+
+	mutex_unlock(&fb_info->bl_curve_mutex);
+}
+EXPORT_SYMBOL_GPL(fb_bl_default_curve);
+#endif