Re: [Oe] Re: /proc/sys/board patch for SIMpad

Am Fr, den 17.09.2004 schrieb Till Harbaum um 14:31:
> Hi,
Hi!

> On Friday 17 September 2004 11:47, Michael 'Mickey' Lauer wrote:
> > Wouldn't it be nice override the kernels behaviour for some special
> > purposes?
> I just checked this. The only routine in the simpads kernel touching the led 
> is simpad_leds_event/leds_event. It looks like these are called during 
> initialisation and during suspend/resume which looks fine to me.
> 
> But this routine is also called e.g. whenever the cpu is idle. And whenever 
> simpad_leds_event is called, it updates the state of the green led (instead 
> of only updating the hardware state if the event is led_start/led_stop).

This should stop when another driver, e.g. the user-space access driver
that is to be written, claims the LEDs. So the driver would have to send
an LED event to claim the LED when the user wants to control it and
release it when done (e.g. on open() and release()).

> So the kernel sets the led state every few milliseconds and thus preventing 
> user space apps from chaning the state permanently.
> 
> The question is: Do we really want this led to be user accessible? If a 
> program switches the display and led off, the user might think the simpad is 
> in suspend, while it's in fact powered up and e.g. draining the battery.

Ah... think of screensaver for example.
Or applications where you want your SIMpad (or device in general) to be
still running but do not need the display. You would then want the
display backlight to be switched off in order to conserve power.

> Ciao,
>   Till
CU
  nils faerber

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