[systemd-devel] [PATCH] backlight: do nothing if max_brightness is 0

[Lennart Poettering]

On Thu, 27.03.14 23:41, Thomas Bächler (thomas at archlinux.org) wrote:

> On virtually any newer Asus mainboard, the eeepc-wmi driver is loaded.
> It exposes a backlight device despite the lack of any physical backlight
> devices. This fake backlight device has max_brightness set to 0. Since
> the introduction of the clamp_brightness function, systemd-backlight
> tries to write '1' to brightness and fails.
> 
> This patch changes systemd-backlight to exit gracefully when
> max_brightness is 0 before performing any action. This affects
> both the load and save actions.

Humm. To me this appears like the driver is broken. The kernel should
not expose a backlight device if there isn't any backend to it? Have you
filed a kernel bug?

I have changed git now to still print a warning in this case, as we
shouldn't silently tape over broken drivers.

Lennart

-- 
Lennart Poettering, Red Hat