driver_vive: clear_halt before submit_transfer in AttachInterface

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Summary

AttachInterface calls libusb_submit_transfer() without first clearing any halt condition on the endpoint. If the endpoint is stalled — from a previous session, a failed transfer, or a device re-enumeration — the submit returns LIBUSB_ERROR_PIPE (-9) and the interface attachment fails silently.

Demonstration

BEFORE — AttachInterface in src/driver_vive.c:

iface->last_submit_time = OGGetAbsoluteTimeUS();
int rc = libusb_submit_transfer(tx);
if (rc) {
    SV_ERROR(SURVIVE_ERROR_HARWARE_FAULT, "Error: Could not submit transfer …");
    return 6;
}

AFTER:

iface->last_submit_time = OGGetAbsoluteTimeUS();

libusb_clear_halt(devh, endpoint_num);

int rc = libusb_submit_transfer(tx);

Impact

Without this, any stalled endpoint causes AttachInterface to fail with LIBUSB_ERROR_PIPE. The device appears to open successfully but receives no data. The fix matches standard libusb practice: always clear halt before the first submit.

Change

One call to libusb_clear_halt(devh, endpoint_num) before libusb_submit_transfer() in the libusb path of AttachInterface.

Found via

Observed on hardware after device re-enumeration left an endpoint halted; libusb_submit_transfer returned -9 and tracking never started.