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DESCRIPTION

It is divided into a machine independent, high-level part responsible for managing device files, and low-level hardware drivers.

The high-level radio driver attaches to the low-level driver when the latter calls radio_attach_mi().

The radio_hw_if struct contains pointers to functions provided by the low-level driver. The hdlp argument is a handle to a low-level driver's softc structure. It is sent as the first argument to all the functions in radio_hw_if when the high-level driver calls them. dev is the device struct for the hardware device.

The fields of radio_hw_if are described in some more detail below.

struct radio_hw_if {
	int	(*open)(void *, int, int, struct lwp *);
	int	(*close)(void *, int, int, struct lwp *);
	int     (*get_info)(void *, struct radio_info *);
	int     (*set_info)(void *, struct radio_info *);
	int     (*search)(void *, int);
};

(*open)(sc, flags, fmt, lwp)

Called when the radio device is opened. Optionally, if there is no need to call a driver's function when the device file is opened, NULL should be passed in this field. Returns 0 on success, otherwise an error code.

(*close)(sc, flags, fmt, lwp)

Called when the radio device is closed. Optionally, if there is no need to call a driver's function when the device file is closed, NULL should be passed in thie field. Returns 0 on success, otherwise an error code.

(*get_info)(sc, ri)

Fills the radio_info struct. This function is used to obtain the current state of a hardware device. It is executed as a result of calling RIOCGINFO on a device file managed by the high-level driver. Returns 0 on success, otherwise an error code.

(*set_info)(sc, ri)

Set values from the radio_info struct. This function is used to modify the current state of a hardware device (enable/disable various modes and parameters). It is executed as a result of calling RIOCSINFO on a device file managed by the high-level driver. Returns 0 on success, otherwise an error code.

(*search)(sc, ri)

Initiates automatic search for the radio station. It is executed as a result of calling RIOCSSRCH on a device file managed by the high-level driver. Returns 0 on success, otherwise an error code.