SetupDiGetClassDevs failed with error 13

I use SetupDiGetClassDevs to retrieve how many usb devices are present , the
code is as follows:
//==================================================
DWORD dwFlag = DIGCF_ALLCLASSES | DIGCF_PRESENT;

HDEVINFO hDevInfo = SetupDiGetClassDevs(NULL, "USB", NULL, dwFlag);

if( hDevInfo == INVALID_HANDLE_VALUE )
{
WriteLog("Gerry:hDevInfo = INVALID_HANDLE_VALUE , Last Error:%d",
GetLastError());
return 0;
}
..
..
..
..
..

//=========================================
The code above runs ok when called from normal applications, but
when this code is called from winlogon.exe before any user log on,
SetupDiGetClassDevs failed with error code 13, I really don't know what's
the difference and why this happens, please any one tell me how to solve this.

Hi,

did you read the following line in the documentation:

"To return devices only for a specific device setup class,
do not set DIGCF_ALLCLASSES, and use ClassGuid to
supply the GUID of the device setup class."

"Do NOT set DIGCF_ALLCLASSES",...at first try it without
this Flag,...then we will see,...

I have something that possibly can aid you. Drop
me a few lines if you like. I wont write about it here
because it would look like house advertising, i dont
want that:




Regards

Kerem

--
--
-----------------------
Beste Grüsse / Best regards / Votre bien devoue
Kerem Gümrükcü
Latest Project: http://www.pro-it-education.de/software/deviceremover
Latest Open-Source Projects: http://entwicklung.junetz.de
-----------------------
"This reply is provided as is, without warranty express or implied."

"Gerryson" <> schrieb im Newsbeitrag
news:250D651A-8C97-4835-9BFF-...
> I use SetupDiGetClassDevs to retrieve how many usb devices are present ,
> the
> code is as follows:
> //==================================================
> DWORD dwFlag = DIGCF_ALLCLASSES | DIGCF_PRESENT;
>
> HDEVINFO hDevInfo = SetupDiGetClassDevs(NULL, "USB", NULL, dwFlag);
>
> if( hDevInfo == INVALID_HANDLE_VALUE )
> {
> WriteLog("Gerry:hDevInfo = INVALID_HANDLE_VALUE , Last Error:%d",
> GetLastError());
> return 0;
> }
> .
> .
> .
> .
> .
>
> //=========================================
> The code above runs ok when called from normal applications, but
> when this code is called from winlogon.exe before any user log on,
> SetupDiGetClassDevs failed with error code 13, I really don't know what's
> the difference and why this happens, please any one tell me how to solve
> this.

I don't think he's trying to get devices of a specific setup class. He's
not passing a class GUID. He's using the enumerator parameter to find
devices enumerated by USB.

I believe the reason you are getting the error is because you are calling
the API before the plug and plug service is available. You must wait until
the PnP service has been started before you can start querying devices.
Probably what you want to do is call the function in a loop until it
succeeds (with a timeout for safety).

-Mike

"Kerem Gümrükcü" <> wrote in message
news:#2VaiE$...
> Hi,
>
> did you read the following line in the documentation:
>
> "To return devices only for a specific device setup class,
> do not set DIGCF_ALLCLASSES, and use ClassGuid to
> supply the GUID of the device setup class."
>
> "Do NOT set DIGCF_ALLCLASSES",...at first try it without
> this Flag,...then we will see,...
>
> I have something that possibly can aid you. Drop
> me a few lines if you like. I wont write about it here
> because it would look like house advertising, i dont
> want that:
>
>
>
>
> Regards
>
> Kerem
>
> --
> --
> -----------------------
> Beste Grüsse / Best regards / Votre bien devoue
> Kerem Gümrükcü
> Latest Project: http://www.pro-it-education.de/software/deviceremover
> Latest Open-Source Projects: http://entwicklung.junetz.de
> -----------------------
> "This reply is provided as is, without warranty express or implied."
>
> "Gerryson" <> schrieb im Newsbeitrag
> news:250D651A-8C97-4835-9BFF-...
>> I use SetupDiGetClassDevs to retrieve how many usb devices are present ,
>> the
>> code is as follows:
>> //==================================================
>> DWORD dwFlag = DIGCF_ALLCLASSES | DIGCF_PRESENT;
>>
>> HDEVINFO hDevInfo = SetupDiGetClassDevs(NULL, "USB", NULL, dwFlag);
>>
>> if( hDevInfo == INVALID_HANDLE_VALUE )
>> {
>> WriteLog("Gerry:hDevInfo = INVALID_HANDLE_VALUE , Last Error:%d",
>> GetLastError());
>> return 0;
>> }
>> .
>> .
>> .
>> .
>> .
>>
>> //=========================================
>> The code above runs ok when called from normal applications, but
>> when this code is called from winlogon.exe before any user log on,
>> SetupDiGetClassDevs failed with error code 13, I really don't know
>> what's
>> the difference and why this happens, please any one tell me how to solve
>> this.
>