NumConfigurations Property

项目
09/21/2010

The NumConfigurations property gets the value of the bNumConfigurations field of the device descriptor, as defined in section 9.6.1 of the USB 2.0 specification.

This property is read-only.

Syntax

HRESULT get_NumConfigurations(
  [out, retval]  BYTE *pbNumConfigs
);

Property Value

Caller-allocated space to hold the returned number of configurations.

Error Codes

NumConfigurations returns S_OK if the operation succeeds or E_POINTER if the pbNumConfigs parameter is not a valid pointer.

Remarks

The value for the bNumConfigurations field is taken from the Count property of the ISoftUSBConfigurations interface that the ISoftUSBDevice::Configurations specifies.

The following C++ code example shows how to get the NumConfigurations property.

HRESULT CLoopBackDevice::GetNumerConfigurations(BYTE *pbNumConfigs)
{
HRESULT hr = OK:
 

 if (NULL == m_piDevice)
{
 hr = E_UNEXPECTED;
 goto Exit;
}

 if (NULL == pbNumConfigs)
{
 hr = E_POINTER;
 goto Exit;
}

// Initialize the return parameter
*pbNumConfigs = 0;

// Get the number of configurations
 hr = m_piDevice->get_NumConfigurations (pbNumConfigs);
Exit:
 return hr;
}

Requirements

Header

SoftUSBif.h

通过