Re: USB Device Interface



All this can be done thru documented API calls, there
is absolutely no reason to play with the registry.


Uwe


m4rk.gm4il@xxxxxxxxx wrote:
Hi,

Try this - the easiest way, It worked for me, I dont know if it will work for you.
I also need other's help on this because i dont have all kinds of USB flash storage device to test my service application. If it does work not for you, pls send me an email coz we are on similar situation.

1> monitor for registry changes under the registry key:

HKLM\SYSTEM\CurrentControlSet\Enum\USBSTOR

2> Once a USB device is inserted onto the USB port, changes
on the registry will be notified thru RegNotifyChangeKeyValue() API
or ur service app will have DBT_DEVICEARRIVAL notification.

3> As soon as there were changes, your application should enumerate the
specified registry subkey and then check for the existence of "Control"
subkeyname.

4> The "Control" subkey, will have a "DeviceReference" valuename under it
with a DWORD value data that refers to that device. - what's the use of that
value data ? i really dont know.

5> Get the PARENT Subkey of this branch because it holds the
"ParentIdPrefix" valuename which has a REG_SZ type of value data.

6> We can use this "ParentIdPrefix" in determining the assigned drive of that
newly inserted USB device. We will then scan the value data under the
registry tree:

HKLM\System\MountedDevices

7> We will only search under those Value name starting with
\DosDevices\<drive letter>. Since this is a binary value, we will
get all of its string equivalent then we will search among those
string equivalent where we can find the valuedata of "ParentIdPrefix" which refers to the inserted USB drive. The valuename which holds this value data represent the Drive letter assigned to the USB drive. Remove the "\DosDevices\" string
to produce the drive letter assignment.

8> Once you get the drive letter assignment, we can also get the
disk geometry: ( Disk size, tracks per cylinder, sectors per track, etc. )
of the USB device. - i tried this only on limited device samples.

9> As soon as the USB device is removed from the USB port, the "DeviceReference" value is removed from that Registry tree.

10> The advantages of this technique is that you can enumerate the USB
device even if the flash drive is already inserted even before your service
application has started. - a little tweak will do it.

11> In Windows 2000, you can get the following important information in the registry:

1> USB Friendly Name - the recognizable name for the USB.
2> Class GUID - The GUID for removable media
3> Device Description - the description for the USB, if this is a flash
drive then the description is "Disk Drive".
4> Driver - The generic driver used for this USB.
5> Manufacturer - this does not give accurate information - it usually gives
"(Standard disk drive)" value and not the actual manufacturer of the USB.
6> USB drive - drive letter assignment for this device.

12> if your devt platform is XP or higher, you can also get the serial number.

13> check this site:

http://www.osronline.com/lists_archive/ntdev/thread11983.html



"Ilia Golubev" wrote:

Hi,

I'm writing NT Service that listens device notifications. I am
subscribing on DEV_BROADCAST_DEVICEINTERFACE notifications. After USB
(flash drive or HDD) is connected, I get DBT_DEVICEARRIVAL notification.
The notification contains the string \\?\Description{GUID}. I find the
same string in the registry HKLM\CONFIG\...\DeviceClasses\... But I
cannot know how to get its drive letter?

Any help would be appreciated.

Ilia

.

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