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

[Pierre Willenbrock]

m. allan noah schrieb:
> On Sat, Jan 10, 2009 at 1:11 PM, Pierre Willenbrock
> <pierre at pirsoft.dnsalias.org> wrote:
>> 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.
> 
> Is it possible for a user to press and release the button and have the
> driver 'lose' it if you dont read the GPIO pins during the 'pressed'
> inteval?

Exactly like that. And the windows driver has the same problem.

>> 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.
> 
> 1Hz from sanebuttonsd has generated some complaints about being too
> slow. I think we should bump it up to 2hz, so that might help.
> 
>>>> 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,
> 
> NP-
> 
> allan