Currently the backlight implementation stretches a brightness change over
a period of 100ms. While this is a fine default for PWM backlights, a user
might wish to change this slew time to meet other constraints or even
completely disable it for some backlight devices.
Add a parameter and provide the default value from the backlight device.
Signed-off-by: Lucas Stach <l.stach@xxxxxxxxxxxxxx>
---
drivers/video/backlight-pwm.c | 1 +
drivers/video/backlight.c | 14 ++++++++++++--
include/video/backlight.h | 1 +
3 files changed, 14 insertions(+), 2 deletions(-)
diff --git a/drivers/video/backlight-pwm.c b/drivers/video/backlight-pwm.c
index ec35bd1bc039..43dc2a36dfd2 100644
--- a/drivers/video/backlight-pwm.c
+++ b/drivers/video/backlight-pwm.c
@@ -206,6 +206,7 @@ static int backlight_pwm_of_probe(struct device_d *dev)
pwm_backlight->period = pwm_get_period(pwm_backlight->pwm);
+ pwm_backlight->backlight.slew_time = 100;
pwm_backlight->backlight.brightness_set = backlight_pwm_set;
pwm_backlight->backlight.node = dev->device_node;
diff --git a/drivers/video/backlight.c b/drivers/video/backlight.c
index 09c0e47af6fb..cbb83087a00b 100644
--- a/drivers/video/backlight.c
+++ b/drivers/video/backlight.c
@@ -15,6 +15,15 @@ int backlight_set_brightness(struct backlight_device *bl, int brightness)
if (brightness == bl->brightness_cur)
return 0;
+ if (!bl->slew_time) {
+ ret = bl->brightness_set(bl, brightness);
+ if (ret)
+ return ret;
+
+ bl->brightness_cur = bl->brightness = brightness;
+ return 0;
+ }
+
if (brightness > bl->brightness_cur)
step = 1;
else
@@ -34,10 +43,9 @@ int backlight_set_brightness(struct backlight_device *bl, int brightness)
if (i == brightness)
break;
- udelay(100000 / num_steps);
+ udelay(bl->slew_time * 1000 / num_steps);
}
-
bl->brightness_cur = bl->brightness = brightness;
return ret;
@@ -72,6 +80,8 @@ int backlight_register(struct backlight_device *bl)
dev_add_param_uint32(&bl->dev, "brightness", backlight_brightness_set,
NULL, &bl->brightness, "%d", bl);
+ dev_add_param_uint32(&bl->dev, "slew_time", NULL, NULL, &bl->slew_time,
+ "%d", NULL);
list_add_tail(&bl->list, &backlights);
diff --git a/include/video/backlight.h b/include/video/backlight.h
index 8dc49dc113e3..52f90a761db5 100644
--- a/include/video/backlight.h
+++ b/include/video/backlight.h
@@ -7,6 +7,7 @@ struct backlight_device {
int brightness_cur;
int brightness_max;
int brightness_default;
+ int slew_time; /* time to stretch brightness changes, in ms */
int (*brightness_set)(struct backlight_device *, int brightness);
struct list_head list;
struct device_d dev;
--
2.17.0
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