Add Caps Lock, Num Lock, and Scroll Lock LED synchronization
following Linux 7.1 hid-input.c: hidinput_output_event().
Led state tracking:
- Caps Lock (usage 0x39) → toggles bit 1
- Scroll Lock (usage 0x47) → toggles bit 2
- Num Lock (usage 0x53) → toggles bit 0
SET_REPORT (Output) via XhciClientHandle::device_request():
- PortReqTy::Class, PortReqRecipient::Interface
- bRequest = 0x09 (SET_REPORT)
- wValue = (0x02 << 8) | 0x00 (Output report type, report ID 0)
- wIndex = interface_num
- Data = 1-byte LED state
The SET_REPORT is sent only when the LED state changes (tracked
with last_led_state sentinel). A failed SET_REPORT is logged at
warn level but does not block the input loop.
Cross-reference: Linux 7.1
- drivers/hid/hid-input.c: hidinput_output_event()
- drivers/hid/usbhid/hid-core.c: usbhid_output_report()
- HID 1.11 spec §7.2.1: SET_REPORT request
This means USB keyboards with Caps/Num/Scroll Lock LEDs will now
have their LEDs synchronized with the host lock state.
Red Bear OS
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