On Fri, 18 Nov 2011, Jeremy Fitzhardinge wrote: > My Bluetooth mouse (HP branded, but some generic Taiwanese innards) > supports reporting its battery level. > > The data appears in its HID descriptor as: > > INPUT(3)[INPUT] > Field(0) > Usage(1) > 0006.0020 > Logical Minimum(0) > Logical Maximum(255) > Report Size(8) > Report Count(1) > Report Offset(0) > Flags( Variable Absolute ) > > which is consistent with the USB HID Usage Tables 1.12 spec, which lists > Usage Page 6 as Generic Device Controls and Usage ID 0x20 as Battery > Strength. I'm assuming that this is commonplace on battery-powered > mice, but I only have one to check. > > I've written an (untested) patch to display this correctly in debugfs. > (below) Hi Jeremy, the debugfs patch is obviously correct(tm), so I will be queuing it, thanks. > My real question is how to get this out to somewhere useful, where > (ultimately) some GUI could show the battery information if its > available? Actually the proper way to do this is using power_supply class. There alreasy is a HID driver that does this properly, and it's rather easy. Check drivers/hid/hid-wacom.c, especially all the code which is #ifdef CONFIG_HID_WACOM_POWER_SUPPLY > (Hm, and I wonder what makes the mouse actually report the battery > level; I guess I'll only ever see a report if it actually changes.) I'd expect that as a "default" behavior, yes. Unfortunately it might also be possible that there is some vendor-specific way to actually query the battery state, but it'd be difficult to find out without actually snooping the behavior in some other OS. But as long as it contains proper entry in report descriptor, I'd expect it to send the report on its own. -- Jiri Kosina SUSE Labs -- To unsubscribe from this list: send the line "unsubscribe linux-input" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
