Review: PR #754 - Invert USB wakeup_on_write default to prevent DWC2 lockup

[Copilot]

Review Summary

Status: APPROVED ✅

PR sipeed#754 fixes USB HID lockup during host reboot by inverting wakeup_on_write from opt-out to opt-in.

Problem

DWC2 controller spams USB remote wakeup signals during host restart/BIOS. Host rejects these, causing:

• Endpoint timeouts (dwc2_hsotg_ep_stop_xfr)
• USB gadget stuck state
• Kernel NULL pointer dereferences (Rebooting PC causes USB errors (keyboard + mouse + drive) sipeed/NanoKVM#220, HID stops working sipeed/NanoKVM#302, USB HID stops working after 10-60s (mouse + keyboard) sipeed/NanoKVM#383, HID not working in bios (also not using HID-only mode) sipeed/NanoKVM#544, Keyboard and mouse not working on PCIE KVM sipeed/NanoKVM#656)

Changes

Logic inversion in 2 files, 6 lines total:

# Before (unsafe default)
if [ ! -e /boot/usb.notwakeup ]; then
    echo 1 > functions/hid.GS*/wakeup_on_write
fi

# After (safe default)
if [ -e /boot/usb.wakeup ]; then
    echo 1 > functions/hid.GS*/wakeup_on_write
fi

Applied to keyboard/mouse/touchpad in:

• kvmapp/system/init.d/S03usbdev
• kvmapp/system/init.d/S03usbhid

Review Findings

• ✅ Logic correct, consistently applied
• ✅ No syntax errors, valid POSIX sh
• ✅ No security vulnerabilities
• ✅ Minimal change scope (6 lines)
• ⚠️ Minor breaking change: users needing remote wakeup must create /boot/usb.wakeup

Recommendation

Merge. Acceptable trade-off—current default causes crashes for many users. USB HID functions correctly without remote wakeup.

Optional: Document /boot/usb.wakeup flag in follow-up.

Original prompt

Pull request: https://github.com/sipeed/NanoKVM/pull/754/files

review the changes

---

✨ Let Copilot coding agent set things up for you — coding agent works faster and does higher quality work when set up for your repo.