[systemd-devel] [PATCH] backlight: Do not clamp brightness for LEDs

[Lennart Poettering]

On Thu, 05.06.14 23:59, Denis Tikhomirov (dvtikhomirov at gmail.com) wrote:

Thanks!

Applied!

> 
> On Thu, Jun 05, 2014 at 08:37:20AM +0200, Lennart Poettering wrote:
> > The patch is line-broken, please send an uncorrupted patch!
> I am very sorry, I forgot that my client limits line width. I will use 
> mutt now on.
> > clamp_brightness() clamps the brightness value to the range of the
> > actual device. This is a recent addition that was added to deal with
> > driver updates where the resolution is changed. I don't think this part
> > should be dropped for LED devices. The clamp_brightness() call hence
> > should be called unconditionally, however, internally it should use a
> > different min_brightness value if something is an !backlight devices...
> Thank you for explanation, this sounds very reasonable to me. Please, 
> see updated patch:
> 
> ---
>  src/backlight/backlight.c | 13 ++++++++++---
>  1 file changed, 10 insertions(+), 3 deletions(-)
> 
> diff --git a/src/backlight/backlight.c b/src/backlight/backlight.c
> index 691472c..860cb22 100644
> --- a/src/backlight/backlight.c
> +++ b/src/backlight/backlight.c
> @@ -225,11 +225,13 @@ static unsigned get_max_brightness(struct udev_device *device) {
>  
>  /* Some systems turn the backlight all the way off at the lowest levels.
>   * clamp_brightness clamps the saved brightness to at least 1 or 5% of
> - * max_brightness.  This avoids preserving an unreadably dim screen, which
> - * would otherwise force the user to disable state restoration. */
> + * max_brightness in case of 'backlight' subsystem. This avoids preserving
> + * an unreadably dim screen, which would otherwise force the user to
> + * disable state restoration. */
>  static void clamp_brightness(struct udev_device *device, char **value, unsigned max_brightness) {
>          int r;
>          unsigned brightness, new_brightness, min_brightness;
> +        const char *subsystem;
>  
>          r = safe_atou(*value, &brightness);
>          if (r < 0) {
> @@ -237,7 +239,12 @@ static void clamp_brightness(struct udev_device *device, char **value, unsigned
>                  return;
>          }
>  
> -        min_brightness = MAX(1U, max_brightness/20);
> +        subsystem = udev_device_get_subsystem(device);
> +        if (streq(subsystem, "backlight"))
> +                min_brightness = MAX(1U, max_brightness/20);
> +        else
> +                min_brightness = 0;
> +
>          new_brightness = CLAMP(brightness, min_brightness, max_brightness);
>          if (new_brightness != brightness) {
>                  char *old_value = *value;


Lennart

-- 
Lennart Poettering, Red Hat