SetupDiGetClassDevs and DIGCF_PRESENT

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3 total messages Started by JohnG Thu, 15 May 2008 15:45

#266

Author: JohnG
Date: Thu, 15 May 2008 15:45

28 lines
1710 bytes

Hi,

In sample code below SetupDiGetClassDevs always returns 
INVALID_HANDLE_VALUE. GetLastError() returns 87, which I 
believe is incorrect parameter. If I replace DIGCF_PRESENT  
with DIGCF_PRESENT | DIGCF_ALLCLASSES, the code works however 
when I enumerate the hardware I get much more then just the 
hardware that is currently in the system. Any ideas why I cant 
use only the DIGCF_PRESENT flag? I am trying to query only the 
hardware that is in the system.


HDEVINFO hDevInfo;
SP_DEVINFO_DATA DeviceInfoData;

// Create a HDEVINFO with all present devices.
hDevInfo = SetupDiGetClassDevs(NULL,
	                       NULL, 
               		       NULL,
		               DIGCF_PRESENT );

if (hDevInfo == INVALID_HANDLE_VALUE)
{
       OutputDebugString("INVALID_HANDLE_VALUE");

       return 0;
}

Re: SetupDiGetClassDevs and DIGCF_PRESENT

#268

Author: Bob Gonder
Date: Thu, 15 May 2008 16:50

20 lines
1706 bytes

JohnG wrote:

>In sample code below SetupDiGetClassDevs always returns 
>INVALID_HANDLE_VALUE. GetLastError() returns 87, which I 
>believe is incorrect parameter. If I replace DIGCF_PRESENT  
>with DIGCF_PRESENT | DIGCF_ALLCLASSES, the code works however 
>when I enumerate the hardware I get much more then just the 
>hardware that is currently in the system. Any ideas why I cant 
>use only the DIGCF_PRESENT flag? I am trying to query only the 
>hardware that is in the system.

Read the comment section in the docs here:
http://msdn.microsoft.com/en-us/library/ms792959.aspx

You must either specify a device guid in ClassGuid,
or use DIGCF_ALLCLASSES. So, your use of NULL for
ClassGuid was in fact an incorrect parameter.

See also example code here
http://support.microsoft.com/kb/259695

Re: SetupDiGetClassDevs and DIGCF_PRESENT

#269

Author: JohnG
Date: Fri, 16 May 2008 12:50

2 lines
887 bytes

Thanks again.

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