[PATCH] drm/panel: ld9040: Register a backlight device

[Paul Cercueil]

Register a backlight device to be able to switch between all the gamma
levels.

While this works, and improves the situation, on my device (Galaxy S2
I9100) the screen does not yet look as good as how it did under Android,
independently of the gamma setting. The blacks are washed and look grey,
while they did look perfectly black on Android thanks to the AMOLED
technology.

Signed-off-by: Paul Cercueil <paul at crapouillou.net>
---
 drivers/gpu/drm/panel/panel-samsung-ld9040.c | 40 ++++++++++++++++++++
 1 file changed, 40 insertions(+)

diff --git a/drivers/gpu/drm/panel/panel-samsung-ld9040.c b/drivers/gpu/drm/panel/panel-samsung-ld9040.c
index c4b388850a13..0dd21a809309 100644
--- a/drivers/gpu/drm/panel/panel-samsung-ld9040.c
+++ b/drivers/gpu/drm/panel/panel-samsung-ld9040.c
@@ -8,6 +8,7 @@
  * Andrzej Hajda <a.hajda at samsung.com>
 */
 
+#include <linux/backlight.h>
 #include <linux/delay.h>
 #include <linux/gpio/consumer.h>
 #include <linux/module.h>
@@ -310,8 +311,40 @@ static int ld9040_parse_dt(struct ld9040 *ctx)
 	return 0;
 }
 
+static int ld9040_bl_update_status(struct backlight_device *dev)
+{
+	struct ld9040 *ctx = dev_get_drvdata(&dev->dev);
+
+	ctx->brightness = dev->props.brightness;
+	ld9040_brightness_set(ctx);
+
+	return 0;
+}
+
+static int ld9040_bl_get_intensity(struct backlight_device *dev)
+{
+	if (dev->props.fb_blank == FB_BLANK_UNBLANK &&
+			dev->props.power == FB_BLANK_UNBLANK)
+		return dev->props.brightness;
+
+	return 0;
+}
+
+static const struct backlight_ops ld9040_bl_ops = {
+	.get_brightness = ld9040_bl_get_intensity,
+	.update_status  = ld9040_bl_update_status,
+};
+
+static const struct backlight_properties ld9040_bl_props = {
+	.type = BACKLIGHT_RAW,
+	.scale = BACKLIGHT_SCALE_NON_LINEAR,
+	.max_brightness = ARRAY_SIZE(ld9040_gammas) - 1,
+	.brightness = ARRAY_SIZE(ld9040_gammas) - 1,
+};
+
 static int ld9040_probe(struct spi_device *spi)
 {
+	struct backlight_device *bldev;
 	struct device *dev = &spi->dev;
 	struct ld9040 *ctx;
 	int ret;
@@ -353,6 +386,13 @@ static int ld9040_probe(struct spi_device *spi)
 	drm_panel_init(&ctx->panel, dev, &ld9040_drm_funcs,
 		       DRM_MODE_CONNECTOR_DPI);
 
+
+	bldev = devm_backlight_device_register(dev, dev_name(dev), dev,
+					       ctx, &ld9040_bl_ops,
+					       &ld9040_bl_props);
+	if (IS_ERR(bldev))
+		return PTR_ERR(bldev);
+
 	drm_panel_add(&ctx->panel);
 
 	return 0;
-- 
2.35.1