Hi, On Fri, Mar 03, 2023 at 03:05:41PM -0800, Jason Gerecke wrote: > Apologies for the delay in replying. > > First off: as an immediate action, I'm thinking of changing the Wacom > driver to do lazy creation of the power_supply device. This would mean > that rather than creating it at the same time as the input device, we > would wait until we receive some kind of affirmative indication of a > battery being present. Most Wacom peripherals report battery status in > a "heartbeat" report that is sent every few seconds, so there wouldn't > be much change for the typical user (just a few-second delay between > connecting the hardware and a power_supply device being created). In > the case of the "component" devices that are built into laptops and > other computers, however, the battery status is only reported while > the pen is actually in proximity. For users like you who don't own (or > never use) a pen, this means that our driver would never create a > power_supply device -- preventing GNOME from showing a battery that > isn't relevant. I'm working on a patch set that does this but need a > bit more time to finish it. > > That's only a partial solution, however. If a component user were to > bring a pen into prox even just briefly, then a power_supply device > would be created and not go away until the user reboots. The pen's > battery status will become stale at some point in time though -- > self-discharge, use of the pen on another device, and even just simple > irrelevance if the user hasn't used the pen in a while (do I care that > the pen which I left at home is at 50% battery?). I agree that it > makes sense for userspace to hide the battery after a while due to > things like this. Are there new signals that the kernel should be > providing to userspace (e.g. an attribute that indicates if we're in > communication with power_supply? an attribute signaling that data > might be stale)? Or are the signals that are already provided > sufficient (e.g. should GNOME just hide power_supply devices that are > in an "Unknown" state? or maybe hide power_supplies which haven't been > updated in more than 1 hour?) Can't you just unregister the power-supply device if there hasn't been any heartbeat for some minutes and go back to the init state (i.e. the one where you are waiting for a heartbeat to appear for the first time)? > I've added the power_supply list and maintainer for some additional > viewpoints on the second paragraph... If there are questions about how > the Wacom hardware and its battery reporting works, I'm happy to > provide answers... I think the problem you have is quite specific to the Wacom hardware. Usually wireless devices are either connected or disconnected and drivers unregister the battery device on disconnect. So I think this logic belongs into Wacom specific code and not in generic power-supply core code. -- Sebastian
Attachment:
signature.asc
Description: PGP signature
