Re: [PATCH] eeepc-wmi: new driver for WMI based hotkeys on Eee PC laptops

[cascardo@holoscopio.com]

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On Sat, Mar 20, 2010 at 08:55:53AM +0800, Yong Wang wrote:
> On Fri, Mar 19, 2010 at 03:23:23PM +0000, Matthew Garrett wrote:
> > 
> > > > > +		if (code >= NOTIFY_BRNUP_MIN && code <= NOTIFY_BRNUP_MAX)
> > > > > +			code = NOTIFY_BRNUP_MIN;
> > > > > +		else if (code >= NOTIFY_BRNDOWN_MIN && code <= NOTIFY_BRNDOWN_MAX)
> > > > > +			code = NOTIFY_BRNDOWN_MIN;
> > > > 
> > > > Do the brightness keys just send notifications, or do they actually 
> > > > change the brightness? If they actually change the brightness, we 
> > > > shouldn't send input events.
> > > > 
> > > 
> > > Yes, hardware and bios change brightness by themselves without software intervention
> > > on my Eee PC 1005 when pressing the hotkeys.
> > 
> > Ok. In that case, you shouldn't send input events. Once backlight 
> > control is implemented in the eee-wmi driver you can send notifications 
> > via that instead.
> > 
> 
> One question just popped off the top my head. What if there is a power
> applet that wants to display a slider field at the bottom of the screen
> showing the current brightness real time whenever users press brightness
> hotkeys? Shouldn't it listen to the standard input events translated by
> X into standard XF86 keysyms? Or shall it listen to the ACPI backlight
> events? If so, it is the ACPI LCD event when using acpi backlight
> driver. But what if those vendor specific backlight drivers are used?
> 
> Thanks
> -Yong
> --

You may select/poll for the sysfs file actual_brightness. It will return
POLLPRI. Basically, backlight devices end up calling sysfs_notify that
will allow sysfs_poll to work. Read the comments about sysfs_poll at
fs/sysfs/file.c.

You should either use backlight_force_update in your driver or let the
user update it writing to the brightness file. In your case, I'd say you
should use backlight_force_update and give BACKLIGHT_UPDATE_HOTKEY as
the reason.

Regards,
Cascardo.

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