使用WINAPI检测USB存储连接

Question

I'm basically trying to detect a simple USB detection and retrieve certain information from it.

Doing so, for a regular USB FLASH drive is quite simple, as most of the MSDN samples show.

HDEVNOTIFY hDevNotify;
DEV_BROADCAST_DEVICEINTERFACE NotificationFilter;
ZeroMemory( &NotificationFilter, sizeof(NotificationFilter) );
NotificationFilter.dbcc_size = sizeof(DEV_BROADCAST_DEVICEINTERFACE);
NotificationFilter.dbcc_devicetype = DBT_DEVTYP_DEVICEINTERFACE;
NotificationFilter.dbcc_classguid = GUID_DEVINTERFACE_USB_DEVICE;
hDevNotify = RegisterDeviceNotification(hWnd, &NotificationFilter, DEVICE_NOTIFY_WINDOW_HANDLE);

and later on, wait for a WM_DEVICECHANGE message with DBT_DEVICEARRIVAL

i actually get 2 sequential messages:

dbcc_name of the first message :

\\\\?\\USB#VID_0781&PID_5597#4C530001210518100555#{a5dcbf10-6530-11d2-901f-00c04fb951ed}

dbcc_name of the second message:

\\?\USBSTOR#Disk&Ven_SanDisk&Prod_Cruzer_Glide_3.0&Rev_1.00#4C530001210518100555&0#{53f56307-b6bf-11d0-94f2-00a0c91efb8b}

From this one, i can actually retrieve the friendaly name and so on.

Now, my problem occurs when i try to do the same with phone connection.

When i plug my phone using a regular USB cable, i get

\\?\USB#VID_18D1&PID_4EE2#00c5c6f0839a25d4#{a5dcbf10-6530-11d2-901f-00c04fb951ed}

SetupDiGetDeviceRegistryProperty with SPDRP_DEVICEDESC returns USB Composite Device

And when i grant file transfer storage permissions on my mobile, i get a second message with:

 \\?\USB#VID_18D1&PID_4EE2#00c5c6f0839a25d4#{a5dcbf10-6530-11d2-901f-00c04fb951ed}

without a friendly name, using the

SetupDiGetDeviceRegistryProperty(hDevInfo, &spDevInfoData, 
            SPDRP_DEVICEDESC, &DataT, (PBYTE)buf, sizeof(buf), &nSize)

function.

So couple of questions here:

1. How does windows recognize this as a mobile device, and even shows its name in the notifications bar ( Nexus 5x , Select to choose what happens with this device)?

2. Lets say i would like to copy certain files from or to it. how do i get device handle or device path for WriteFile / CreateFile

3. How come GetLogicalDrivesStrings retrieves a new drive(" c:\\\\\\0d:\\\\\\0 ") for a regular USB flash drive but doesn't do the same for mobile connection?

Answer 1

Look at the dialog on your phone. You probably picked an option named "MTP". This is a file sharing protocol. On the other hand, the USB stick uses a block storage protocol. That's why you get the USBSTOR announcement.

Block storage allows for dumb devices, and requires intelligence on the host (Windows). It's just a few million 512-byte sectors. Turning that into files is the responsibility of the FAT (or NTFS) driver.

Since block storage uses the FAT driver, it gets a drive letter just like internal hard disks, and can be accessed via CopyFile . Since MTP devices aren't managed by the file system, they don't have drive letters.

Why do mobile phones use MTP then? The big advantage is that MTP allows the phone to be much more in control. It can decide on a file by file basis whether to show it to the USB host.

(Disclosure: you can do that with FAT as well, but my former employer may still have a patent on that. Search for "Data storage access device patent TomTom" if this matters to you)

Answer 2

when a smartphone is connected it appears at first as a SCSI device. then USB protocol supports several attributes (beside vendorID and productID ) from that an operating system can get informations like the device name ( NEXUS 5x ,...) for this especially the attribute fields manufacturer and product

so windows does not 'know' it is a smartphone

the following is the output of udevadm info -a -p /sys/class/scsi_host/... on linux:

looking at device '/devices/pci0000:00/0000:00:12.2/usb1/1-3/1-3:1.0/host42/scsi_host/host42':
    KERNEL=="host42"
    SUBSYSTEM=="scsi_host"
    DRIVER==""
    ATTR{unique_id}=="0"
    ATTR{host_busy}=="0"
    ATTR{cmd_per_lun}=="1"
    ATTR{can_queue}=="1"
    ATTR{sg_tablesize}=="65535"
    ATTR{sg_prot_tablesize}=="0"
    ATTR{unchecked_isa_dma}=="0"
    ATTR{proc_name}=="usb-storage"
    ATTR{state}=="running"
    ATTR{supported_mode}=="Initiator"
    ATTR{active_mode}=="Initiator"
    ATTR{prot_capabilities}=="0"
    ATTR{prot_guard_type}=="0"

  looking at parent device '/devices/pci0000:00/0000:00:12.2/usb1/1-3/1-3:1.0/host42':
    KERNELS=="host42"
    SUBSYSTEMS=="scsi"
    DRIVERS==""

  looking at parent device '/devices/pci0000:00/0000:00:12.2/usb1/1-3/1-3:1.0':
    KERNELS=="1-3:1.0"
    SUBSYSTEMS=="usb"
    DRIVERS=="usb-storage"
    ATTRS{bInterfaceNumber}=="00"
    ATTRS{bAlternateSetting}==" 0"
    ATTRS{bNumEndpoints}=="02"
    ATTRS{bInterfaceClass}=="08"
    ATTRS{bInterfaceSubClass}=="06"
    ATTRS{bInterfaceProtocol}=="50"
    ATTRS{supports_autosuspend}=="1"
    ATTRS{interface}=="Mass Storage"

  looking at parent device '/devices/pci0000:00/0000:00:12.2/usb1/1-3':
    KERNELS=="1-3"
    SUBSYSTEMS=="usb"
    DRIVERS=="usb"
    ATTRS{configuration}==""
    ATTRS{bNumInterfaces}==" 1"
    ATTRS{bConfigurationValue}=="1"
    ATTRS{bmAttributes}=="c0"
    ATTRS{bMaxPower}=="500mA"
    ATTRS{urbnum}=="195"
    ATTRS{idVendor}=="feed"
    ATTRS{idProduct}=="2002"
    ATTRS{bcdDevice}=="ffff"
    ATTRS{bDeviceClass}=="00"
    ATTRS{bDeviceSubClass}=="00"
    ATTRS{bDeviceProtocol}=="00"
    ATTRS{bNumConfigurations}=="1"
    ATTRS{bMaxPacketSize0}=="64"
    ATTRS{speed}=="480"
    ATTRS{busnum}=="1"
    ATTRS{devnum}=="34"
    ATTRS{devpath}=="3"
    ATTRS{version}==" 2.00"
    ATTRS{maxchild}=="0"
    ATTRS{quirks}=="0x0"
    ATTRS{avoid_reset_quirk}=="0"
    ATTRS{authorized}=="1"
    ATTRS{manufacturer}=="MediaTek"
    ATTRS{product}=="X5"
    ATTRS{serial}=="0123456789ABCDEF"

then it depends what function you activate on your smartphone. if you want to activate tethering windows will get notified by the android device and load the RNDIS driver. the notification mechanism is a rest of the USB connection

if you want to write or read files from the androids mass storage you have to activate the mass storage option and windows will get notified and 'mount' the android as a file system

so an android has implemented multiple interfaces / USB device classes in its USB structure and the user has to choose which interface to activate (tethering -> RNDIS, storage -> USB mass storage class,...)

this is also the reason why no new drive c:\\\\\\0d:\\\\\\0 appears when you connect the android to windows. At first the android appears as a SCSI device with no specified function (SCSI Target)

For communication with the android in SCSI mode see http://www.stackoverflow.com/questions/3316284/sending-a-specific-scsi-command-to-a-scsi-device-in-windows

if you want to read or write the phones (internal, SD card) activate the mass storage option and you can use the normal USB mass storage interface (like USB memory stick)

for getting the dbcc_name maybe see http://www.stackoverflow.com/questions/2208722/how-to-get-friendly-device-name-from-dev-broadcast-deviceinterface-and-device-in