[sane-devel] buttons-daemon for SANE genesys scanner

[Pierre Willenbrock]

m. allan noah schrieb:
> On Fri, Jan 9, 2009 at 5:02 PM, Pierre Willenbrock
> <pierre at pirsoft.dnsalias.org> wrote:
[...]
> 
>> Another question: Is it okay to only look at the hardware state if the
>> frontend asks for the state of the option? That way shorter presses can
>> be lost, if the frontend does not poll often enough.
> 
> In my case, the scanners are smart enough to buffer the button presses
> for 3 seconds, and I effectively read the status of all the buttons
> from the scanner every time you ask for the value of the first option.
> So, as long as the front-end reads within that 3 second window, no
> presses are lost.
> 
> If your machines dont buffer, then you might need a thread just to
> read the status really quickly? Do you know how frequently the windows
> driver reads the buttons?

The genesys chips don't help at detecting hardware buttons. The only
sensor logic in the chip is for the home-sensor. The rest is GPIO.
The windows driver polls at 2Hz, this is not much better than the
polling frequency of sanebuttonsd(1Hz). I'll go for the non-threaded
variant for now, while making the logic work if the polling function is
called more often than the sane options are looked at.

>> Before i start to ask more similar questions: Is this documented
>> somewhere? I looked at the html-version of the standard, but could only
>> find the capabilities thing for buttons.
> 
> Nothing is documented. Everything we are discussing now came about
> from prior threads on this list, and thru several iterations of button
> support and button daemon work i did for users of the fujitsu backend.
> IOW, this might not work for your scanners, so we should modify it if
> required.

Thanks for your answers,
  Pierre