usbdevice: hardcoded android0 breaks after gadget directory recreation

[frankurcrazy]

Bug Description

/usr/bin/usbdevice hardcodes android0 when reading the USB gadget state at line 519:

USB_STATE=$(cat /sys/class/android_usb/android0/state)

The kernel uses a monotonic counter (gadget_index++) in drivers/usb/gadget/configfs.c (android_device_create()) to name android_usb devices. If the configfs gadget directory (/sys/kernel/config/usb_gadget/rockchip) is removed with rmdir and recreated, the new device is named android1 instead of android0, because the counter is never decremented.

This causes usbdevice update to silently fail — USB_STATE becomes empty, and any logic that depends on the gadget state (e.g., UMS mount/unmount in ums_start()) misbehaves.

Root Cause

In drivers/usb/gadget/configfs.c:

static int gadget_index;  // never decremented

static int android_device_create(struct gadget_info *gi)
{
    gi->dev = device_create(android_class, NULL,
            MKDEV(0, 0), NULL, "android%d", gadget_index++);
    // ...
}

Source: https://github.com/LubanCat/kernel/blob/a5b4e9f62f94f1865ab8c3d86be7d9168f3da406/drivers/usb/gadget/configfs.c#L1776

Fix

Use a glob instead of hardcoding android0:

USB_STATE=$(cat /sys/class/android_usb/android*/state 2>/dev/null | head -1)

This works regardless of which androidN device exists.

Environment

• Board: RK3588 (LubanCat)
• Kernel: 5.10.160