On δΊ”, 2012-05-18 at 09:53 +0200, Corentin Chary wrote:
> Len, Zhang, you may have an advice on that:
> - vendor backlight interface provides a working "power" file
> - generic backlight interface does not
> - hardware send a notification when the user press the LCD toogle key
>
> Solutions:
> - Use acpi_video=vendor by default (adding a blacklist in ACPI code)
yes, I agree.
> - Handle the key in the driver instead of letting userspace do it
well, I don't know.
when using acpi_video=vendor, what action is taken in userspace after
pressing the key?
thanks,
rui
> - Another idea ?
>
> > Userspace app, such as gnome-settings-daemon, will use
> > /sys/class/backlight/acpi_video0
> > as it's first choice if there is one.
> > But ACPI function to toggle the backlight power is not working, and
> > from our BIOS engineer,
> > ACPI doesn't define the backlight power section, but ASUS WMI does.
> > So, I think it would have less problem to turn on/off backlight power
> > through WMI.
>
> Ok. So the vendor backlight provides features that the generic
> backlight does not.
>
>
> > And, yes, calling asus_wmi_backlight_init() is not a good idea here.
> > We have to record the backlight power status by ourselves if we didn't call
> > it.
> > Let me show you another version of patch later.
>
> That's a solution yes. Another one could be to force
> acpi_backlight=vendor for these well known laptop, but I don't know if
> this will be accepted by ACPI maintainers. So let's start with a
> simpler patch as you proposed (handling via backlight if registered,
> or recording the status ourselve if it's not the case, but please add
> a comment explaining why it's done this way).
>
> >> What does the key do exactly without driver ? Does it just send a
> >> notification or does it also poke the hardware ?
> > It's a WMI event notify, and will be mapped to the key shown below
> > { KE_KEY, 0xe9, { KEY_BRIGHTNESS_ZERO } },
> > Just a notification.
>
> KEY_DISPLAY_TOGGLE is the key to power up/down an LCD screen. Looks
> better than KEY_BRIGHTNESS_ZERO that may only put the brughtness to
> zero. But I'm not sure how these keys are handled by userspace.
>
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