func SelectStorages(dev *mtp.Device, pat string) ([]uint32, error) {
	sids := mtp.Uint32Array{}
	err := dev.GetStorageIDs(&sids)
	if err != nil {
		return nil, err
	}

	re, err := regexp.Compile(pat)
	if err != nil {
		return nil, err
	}

	filtered := []uint32{}
	for _, id := range sids.Values {
		var s mtp.StorageInfo
		err := dev.GetStorageInfo(id, &s)
		if err != nil {
			return nil, err
		}

		if !s.IsHierarchical() {
			log.Printf("skipping non hierarchical storage %q", s.StorageDescription)
			continue
		}

		if re.FindStringIndex(s.StorageDescription) == nil {
			log.Printf("filtering out storage %q", s.StorageDescription)
			continue
		}
		filtered = append(filtered, id)
	}

	return filtered, nil
}

// DeviceFs is a simple filesystem interface to an MTP device. It
// should be wrapped in a Locking(Raw)FileSystem to make sure it is
// threadsafe.  The file system assumes the device does not touch the
// storage.  Arguments are the opened mtp device and a directory for the
// backing store.
func NewDeviceFSRoot(d *mtp.Device, storages []uint32, options DeviceFsOptions) (nodefs.Node, error) {
	root := rootNode{Node: nodefs.NewDefaultNode()}
	fs := &deviceFS{
		root:    &root,
		dev:     d,
		options: &options,
	}
	root.fs = fs
	fs.storages = storages
	if err := d.GetDeviceInfo(&fs.devInfo); err != nil {
		return nil, err
	}

	if !strings.Contains(fs.devInfo.MTPExtension, "android.com") {
		fs.options.Android = false
	}

	if !options.Android {
		if err := fs.setupClassic(); err != nil {
			return nil, err
		}
	}

	fs.mungeVfat = make(map[uint32]bool)
	for _, sid := range fs.storages {
		var info mtp.StorageInfo
		if err := fs.dev.GetStorageInfo(sid, &info); err != nil {
			return nil, err
		}
		fs.mungeVfat[sid] = info.IsRemovable() && fs.options.RemovableVFat
	}

	return fs.Root(), nil
}

// DeviceFs is a simple filesystem interface to an MTP device. It
// should be wrapped in a Locking(Raw)FileSystem to make sure it is
// threadsafe.  The file system assumes the device does not touch the
// storage.  Arguments are the opened mtp device and a directory for the
// backing store.
func NewDeviceFs(d *mtp.Device, storages []uint32, options DeviceFsOptions) (*DeviceFs, error) {
	root := rootNode{}
	fs := &DeviceFs{root: &root, dev: d, options: &options}
	root.fs = fs
	fs.storages = storages
	err := d.GetDeviceInfo(&fs.devInfo)
	if err != nil {
		return fs, nil
	}

	if !strings.Contains(fs.devInfo.MTPExtension, "android.com") {
		fs.options.Android = false
	}

	if !options.Android {
		err = fs.setupClassic()
		if err != nil {
			return nil, err
		}
	}

	fs.mungeVfat = make(map[uint32]bool)
	for _, sid := range fs.storages {
		var info mtp.StorageInfo
		if err != nil {
			return nil, err
		}

		fs.mungeVfat[sid] = info.IsRemovable() && fs.options.RemovableVFat
	}

	return fs, nil
}

// DeviceFs is a simple filesystem interface to an MTP device. It
// should be wrapped in a Locking(Raw)FileSystem to make sure it is
// threadsafe.  The file system assumes the device does not touch the
// storage.  Arguments are the opened mtp device and a directory for the
// backing store.
func NewDeviceFs(d *mtp.Device, storages []uint32, options DeviceFsOptions) (*DeviceFs, error) {
	o := options

	root := rootNode{}
	fs := &DeviceFs{root: &root, dev: d, options: &o}
	root.fs = fs
	fs.storages = storages
	err := d.GetDeviceInfo(&fs.devInfo)
	if err != nil {
		return fs, nil
	}

	if !strings.Contains(fs.devInfo.MTPExtension, "android.com") {
		return nil, fmt.Errorf("this device has no android.com extensions.")
	}

	for _, sid := range fs.storages {
		var info mtp.StorageInfo
		err := d.GetStorageInfo(sid, &info)
		if err != nil {
			return nil, err
		}
		fs.storageInfos = append(fs.storageInfos, info)
	}
	return fs, nil
}