[Bug 222229] HID: usbhid: Razer DeathStalker Essential 2014 (1532:011f) 51.2s EP0 initialization timeout (-110), dead LEDs, and hotplug failure

[bugzilla-daemon@kernel.org]

https://bugzilla.kernel.org/show_bug.cgi?id=222229

--- Comment #1 from Pierre LEROY (pierre.jap@gmail.com) ---
    UPDATE / FINAL SOLUTION:

    After further usbmon trace analysis and prototyping, the exact root causes
and a verified 100% working fix for the 51.2s timeout, dead
    status LEDs, and hotplug failures have been identified:

    1. Root Causes:
       - Destabilization on GET_REPORT: The MCU EP0 parser wedges if
usbhid_init_reports() queries reports via EP0 (requires
       HID_QUIRK_NO_INIT_REPORTS | HID_QUIRK_NOGET).
       - Dirty EP0 state: After usbhid_parse() queries class
GET_DESCRIPTOR(HID_DT_REPORT) (0x81), EP0 hangs on immediate subsequent
requests.
       Issuing a standard 18-byte GET_DESCRIPTOR(USB_DT_DEVICE) (0x80) on EP0
before and after usbhid_parse() resets the MCU state machine
       cleanly.
       - Asynchronous led_work race: When Interface 0 (1.0) finishes
input_register_device(), input_leds_connect() schedules hdev->led_work
       asynchronously on system_wq. This sends HID_REQ_SET_REPORT over EP0 at
the exact same millisecond usb_set_configuration() begins probing
       Interface 1 (1.1) on EP0, resulting in 2 x 25.6s = 51.2s ETIMEDOUT.
       - Hardware LED routing: The hardware status LEDs (NumLock / CapsLock /
ScrollLock) are actually accepted and routed through Interface 1
       (1.1, the NKRO keyboard interface), not Interface 0.

    2. Verified Results:
       With EP0 descriptor resets, flushing led_work prior to probing secondary
interfaces, and routing LEDs to Interface 1.1:
       - USB HID enumeration drops from 51.2s to < 0.2s.
       - All 3 interfaces (1.0 Boot Keyboard, 1.1 NKRO Keyboard, 1.2
Mouse/Vendor) bind cleanly.
       - NumLock, CapsLock, and ScrollLock LEDs light and toggle immediately.
       - Hotplugging (unplug / replug) is 100% reliable.

    3. Working Reference Module & Code:
       Full DKMS module and verification code:
       https://github.com/Djkawada/razer-deathstalker-linux-fix

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