Linux iso transfers crash Chromium with `Invalid argument (22)` — missing `selectAlternateInterface` after `claimInterface`

[turbocrime]

Summary

Camera.setMode({ depth: ... }) causes the Chromium USB utility process to crash on Linux. The same code works on macOS Chromium. Root cause is a missing dev.selectAlternateInterface(...) call after dev.claimInterface(...) in the camera worker.

Environment

• OS: Fedora Asahi (Apple Silicon)
• Browser: Chromium (Linux)
• Device: Xbox 360 Kinect, vid 045e pid 02ae
• @webnect/driver: 0.1.1
• Host pre-reqs already in place: gspca_kinect blacklisted/unloaded, libfreenect-style udev rules granting user access to vid 045e. The device opens cleanly — no Access denied.

Symptom

chromium-browser.log excerpt at the moment Camera.setMode runs:

USB: usb_device_handle_usbfs.cc:168 Low-level transfer error: Invalid argument (22)
crashpad/snapshot/elf/elf_dynamic_array_reader.h:64 tag not found
crashpad/snapshot/elf/elf_dynamic_array_reader.h:64 tag not found
crashpad/snapshot/elf/elf_dynamic_array_reader.h:64 tag not found
crashpad/snapshot/elf/elf_dynamic_array_reader.h:64 tag not found

EINVAL from usbfs on URB submission, then crashpad fires ~25 ms later — the iso transfer takes down the USB process before the JS-side isochronousTransferIn() rejection can surface.

Same code paths on macOS Chromium stream depth frames without issue.

Root cause

In src/camera/worker/worker.ts, getDevice does:

if (!iface.claimed) {
  await dev.claimInterface(usbInterface);
}
return dev;

…and the caller goes straight into dev.isochronousTransferIn(...) via UnderlyingIsochronousTransferSource. Grep across src/ confirms there is zero selectAlternateInterface / alternateSetting usage anywhere in the driver.

macOS's IOUSBLib is permissive about this — it'll accept an iso transfer with the interface in its default alt setting. Linux's usbfs requires an explicit SET_INTERFACE ioctl to reserve iso bandwidth for the endpoint; without it the URB submission returns EINVAL and the Chromium USB utility process crashes (this isn't a graceful JS-level rejection on Linux — it kills the worker process).

Suggested fix

Add an explicit alt-setting selection after the claim:

if (!iface.claimed) {
  await dev.claimInterface(usbInterface);
}
await dev.selectAlternateInterface(usbInterface, 0);
return dev;

libfreenect src/cameras.c calls libusb_set_interface_alt_setting(udev->cam, 0, 0) for the camera interface, so alt 0 is the right starting point. Worth verifying against the device's USB descriptor in case the iso endpoints actually live on a different alt — if so, use that one.

Notes

macOS users won't observe a regression after this fix lands; it's a no-op on platforms that already tolerate the missing call.