Hi Lucas,
On Mon, May 07, 2018 at 04:46:31PM +0200, Lucas Stach wrote:
> 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 */
Just a suggestion: Maybe call this variable and the device parameter
"slew_time_ms" or "slew_time_in_ms". This way a developer does not have
to lookup the unit of the time value in the source code or have to guess
whether the value is in milli-, micro- or just seconds.
Kind regards,
Stefan
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