SDIO - Secure Digital Input Output is a standard for communicating with various external devices such as Wifi and bluetooth devices.
The driver is currently designed to only support communication with certain Cypress Wifi and Bluetooth chipsets, it is not designed to work with a general SDIO card, or even and SD card. It is only intended to be used by the WiFi driver for communication.
This is not intended to be used as a general purpose API.
Always Four Wire Mode
Supports Card Interrupt
Uses DMA for command and data transfer