Several different types of device drivers are Card Services clients. Any 32-bit protect mode device driver that uses Card Services 2.x will work under Windows 95. However, without some changes, resource allocation may not be optimized, and the device driver does not participate in any resource balancing. Because the device driver makes the requests for resources and configuring the card, this may be the only option to support cards with an incomplete card information structure (CIS).
For cards with complete CIS information, these drivers can still benefit from an optimized initial resource allocation. Upon card insertion, the PCMCIA bus enumerator reads the card's CIS to determine the card's resource requirements. If the PCMCIA bus enumerator is successful (that is, if the CIS is complete), it builds the resource request list on behalf of the client driver. This enables the Configuration Manager to find a working resource allocation. Once the Card Services portion of the PCCARD module is told what resources were allocated, it simply filters the client driver's resource requests until it requests the correct preallocated resources.