Multi-Function Cards
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8/28/2008
Multifunction cards refer to Secure Digital I/O (SDIO) cards that implement more than one I/O function. Each function operates in a separate SDIO register space and can be controlled independently.
A multifunction card has a single shared SDIO card controller. The card controller implements a common configuration area that the bus driver can use to query the capabilities of the card and activate common features.
The bus driver creates additional device instance handles, one per function, and loads additional client drivers for each function. The bus driver loads client drivers based on registry keys defined for the interface class or for undefined classes and checks for a custom ID key.
Each client driver is unaware of the existence of the functions and can operate independently. If one of the functions in a multifunction device is not supported, the bus driver will still allow other supported functions to operate normally.
The following illustration shows how a multifunction card is structured.
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