[systemd-devel] [PATCH] backlight: let the administrator override clamping

[David Herrmann]

Hi

On Sat, Jan 17, 2015 at 12:28 PM, Topi Miettinen <toiwoton at gmail.com> wrote:
> On my computer, the minimum brightness enforced by clamping in
> backlight is too bright.

How can 5% of the backlight be "too bright"? Can you give some
information on your backlight device? (type, max_brightness,
actual_brightness and so on).

Btw., we use gnu-getopt_long() style arguments with two dashes. And we
try to avoid negations in option names.

Thanks
David

> Add a new option to override clamping in unit file. While at it, describe
> the clamping in documentation.
> ---
>  man/systemd-backlight at .service.xml | 23 +++++++++++++++++++++--
>  src/backlight/backlight.c          | 11 ++++++-----
>  2 files changed, 27 insertions(+), 7 deletions(-)
>
> diff --git a/man/systemd-backlight at .service.xml b/man/systemd-backlight at .service.xml
> index 453afbf..26a2437 100644
> --- a/man/systemd-backlight at .service.xml
> +++ b/man/systemd-backlight at .service.xml
> @@ -48,7 +48,17 @@
>
>          <refsynopsisdiv>
>                  <para><filename>systemd-backlight at .service</filename></para>
> -                <para><filename>/usr/lib/systemd/systemd-backlight</filename></para>
> +                <cmdsynopsis>
> +                        <command>systemd-backlight</command>
> +                        <arg choice="plain">save</arg>
> +                        <arg choice="opt"><replaceable>PATH</replaceable></arg>
> +                </cmdsynopsis>
> +                <cmdsynopsis>
> +                        <command>systemd-backlight</command>
> +                        <arg choice="plain">load</arg>
> +                        <arg choice="opt"><replaceable>PATH</replaceable></arg>
> +                        <arg choice="opt"><replaceable>-no-clamp</replaceable></arg>
> +                </cmdsynopsis>
>          </refsynopsisdiv>
>
>          <refsect1>
> @@ -58,7 +68,16 @@
>                  is a service that restores the display backlight
>                  brightness at early boot and saves it at shutdown. On
>                  disk, the backlight brightness is stored in
> -                <filename>/var/lib/systemd/backlight/</filename>.</para>
> +                <filename>/var/lib/systemd/backlight/</filename>. During
> +                loading, unless option
> +                <replaceable>-no-clamp</replaceable> is specified, the
> +                brightness is clamped to at least value
> +                <literal>1</literal> or 5% of maximum
> +                brightness.</para>
> +
> +                <para><replaceable>PATH</replaceable> identifies the
> +                display brightness control device. It is resolved by
> +                udev.</para>
>          </refsect1>
>
>          <refsect1>
> diff --git a/src/backlight/backlight.c b/src/backlight/backlight.c
> index 1271a66..a3f71e9 100644
> --- a/src/backlight/backlight.c
> +++ b/src/backlight/backlight.c
> @@ -255,7 +255,7 @@ static void clamp_brightness(struct udev_device *device, char **value, unsigned
>                          return;
>                  }
>
> -                log_info("Saved brightness %s %s to %s.", old_value,
> +                log_info("Saved brightness %s %s to %s (use -no-clamp to override).", old_value,
>                           new_brightness > brightness ?
>                           "too low; increasing" : "too high; decreasing",
>                           *value);
> @@ -272,8 +272,8 @@ int main(int argc, char *argv[]) {
>          unsigned max_brightness;
>          int r;
>
> -        if (argc != 3) {
> -                log_error("This program requires two arguments.");
> +        if (argc < 3 || argc > 4) {
> +                log_error("This program requires two or three arguments.");
>                  return EXIT_FAILURE;
>          }
>
> @@ -389,8 +389,9 @@ int main(int argc, char *argv[]) {
>                          log_error_errno(r, "Failed to read %s: %m", saved);
>                          return EXIT_FAILURE;
>                  }
> -
> -                clamp_brightness(device, &value, max_brightness);
> +                /* Don't clamp brightness if asked */
> +                if (!(argc == 4 && streq(argv[3], "-no-clamp")))
> +                        clamp_brightness(device, &value, max_brightness);
>
>                  r = udev_device_set_sysattr_value(device, "brightness", value);
>                  if (r < 0) {
> --
> 2.1.4
>
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