Re: [PATCH v2 12/33] HID: logitech-hidpp: mark device online on unified battery 0x1004 events

[Dmitry Torokhov <dmitry.torokhov@gmail.com>]

On Wed, Nov 11, 2026 at 08:22:48AM +0000, sashiko-reviews@lists.linux.dev wrote:
> [Severity: High]
> Does this cause a regression on feature 0x1000 devices by overwriting
> hidpp->battery when a charging event arrives, and corrupt 0x1004 events by
> running hidpp20_battery_event_1000() first?
>
> Both feature 0x1000 and feature 0x1004 store their index in
> hidpp->battery.feature_index and use event ID 0x00, and
> hidpp_raw_hidpp_event() calls both handlers unconditionally:
>
> drivers/hid/hid-logitech-hidpp.c:hidpp_raw_hidpp_event() {
> 	...
> 	if (hidpp->capabilities & HIDPP_CAPABILITY_HIDPP20_BATTERY) {
> 		ret = hidpp20_battery_event_1000(hidpp, data, size);
> 		if (ret != 0)
> 			return ret;
> 		ret = hidpp20_battery_event_1004(hidpp, data, size);
> 		if (ret != 0)
> 			return ret;
> 	...
> }
>
> On a 0x1000 device, a charging report sets hidpp->battery.online to false
> in hidpp20_battery_event_1000() and returns 0.  With this change,
> hidpp20_battery_event_1004() then sees !hidpp->battery.online, forces
> changed to true, sets hidpp->battery.online back to true, and overwrites
> capacity, status, and level using 0x1004 decoding, which also prevents the
> 0 to 1 online transition needed to schedule reset_hi_res_work when the
> charging cable is unplugged.
>
> Conversely, on a 0x1004 device, hidpp20_battery_event_1000() runs first on
> every 0x1004 event and mutates hidpp->battery.online before
> hidpp20_battery_event_1004() checks !hidpp->battery.online, setting online
> to false on every charging event and true on discharging or full reconnect
> events.
>
> Gating hidpp20_battery_event_1000() and hidpp20_battery_event_1004() on
> HIDPP_CAPABILITY_UNIFIED_BATTERY would avoid both handlers matching the
> same event.

Good catch! Since both features share hidpp->battery.feature_index and
event ID 0x00, calling both handlers unconditionally causes them to
collide. I will update v3 to gate hidpp20_battery_event_1004() and
hidpp20_battery_event_1000() on HIDPP_CAPABILITY_UNIFIED_BATTERY in
hidpp_raw_hidpp_event(), matching hidpp_connect_event().

Thanks.

-- 
Dmitry