Polling of sensors

One of the discussed features for scanners is the polling of sensors. This arose for me through adding support for buttons for an HP Scanjet 5400C which also has an LCD copy counter the value of which can be manipulated with buttons on the panel. The function of this is to feed into an automated copy function (scan, then print some copies to a pre-nominated printer) that the provided software offers.

However, there is no mechanism within the SANE standard to indicate which sensors are volatile and should be polled regularly for update. xsane allows the value of these sensors to be detected in the interface, but the application has no notion that the value may change as a result of user actions.

For this specific example, we do not have an application that can take advantage of this feature but it is something that I would like to implement perhaps in xsane at some point, or in another application.

Caution has been expressed though that polling of scanners can create undesirable heavy traffic on networks. It might be that the backend should be savvy enough to only advertise the feature through a USB interface and could perhaps specify a recommendation of a polling interval.

Anyway, discussion welcome. I understand that this feature was discussed many moons ago, with no consensus being reached.