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

[David Herrmann]

Hi

On Sat, Jan 17, 2015 at 1:01 PM, Topi Miettinen <toiwoton at gmail.com> wrote:
> On 01/17/15 11:38, David Herrmann wrote:
>> 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).
>
> Well, my eyes start to hurt with level 1, 0 is OK. Max_brightness is 9,
> actual_brightness always matches brightness. This is cheap old Acer
> Aspire 8530 laptop with Mobility Radeon HD 3200, I don't know beyond
> that what handles backlight.

Which backlight driver is active? acpi? Or the native radeon driver?

Thanks
David

>>
>> Btw., we use gnu-getopt_long() style arguments with two dashes. And we
>> try to avoid negations in option names.
>
> Ok. How about --disable-clamping or --allow-low-brightness, or would you
> have better ideas?
>
>>
>> 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
>>>
>>> _______________________________________________
>>> systemd-devel mailing list
>>> systemd-devel at lists.freedesktop.org
>>> http://lists.freedesktop.org/mailman/listinfo/systemd-devel
>