.\"	$NetBSD: radio.9,v 1.6 2018/07/18 16:40:30 wiz Exp $
.\"	$OpenBSD: radio.9,v 1.2 2001/10/08 08:52:50 mpech Exp $
.\"
.\" Copyright (c) Maxim Tsyplakov <tm@oganer.net>
.\" All rights reserved.
.\"
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.Dd July 9, 2018
.Dt RADIO 9
.Os
.Sh NAME
.Nm radio
.Nd interface between low- and high-level FM radio drivers
.Sh SYNOPSIS
.In dev/radio_if.h
.Ft device_t
.Fo radio_attach_mi
.Fa "const struct radio_hw_if *rhwp"
.Fa "void *hdlp"
.Fa "device_t dev"
.Fc
.Sh DESCRIPTION
The
.Nm
layer provides support for digitally programmable FM radio tuners.
.Pp
It is divided into a machine independent, high-level part responsible for
managing device files, and low-level hardware drivers.
.Pp
The high-level radio driver attaches to the low-level driver
when the latter calls
.Fn radio_attach_mi .
.Pp
The
.Fa radio_hw_if
struct contains pointers to functions provided by the low-level driver.
The
.Fa 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
.Fa radio_hw_if
when the high-level driver calls them.
.Fa dev
is the device struct for the hardware device.
.Pp
The fields of
.Fa radio_hw_if
are described in some more detail below.
.Bd -literal
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);
};
.Ed
.Bl -tag -width XXXX
.It Fn (*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,
.Dv NULL
should be passed in this field.
Returns 0 on success, otherwise an error code.
.It Fn (*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,
.Dv NULL
should be passed in thie field.
Returns 0 on success, otherwise an error code.
.It Fn (*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
.Dv RIOCGINFO
on a device file managed by the high-level driver.
Returns 0 on success, otherwise an error code.
.It Fn (*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
.Dv RIOCSINFO
on a device file managed by the high-level driver.
Returns 0 on success, otherwise an error code.
.It Fn (*search) "sc" "ri"
Initiates automatic search for the radio station.
It is executed as a result of calling
.Dv RIOCSSRCH
on a device file managed by the high-level driver.
Returns 0 on success, otherwise an error code.
.El
.Sh SEE ALSO
.Xr radio 4
.Sh AUTHORS
.An -nosplit
The
.Nm
API was written by
.An Vladimir Popov
and
.An Maxim Tsyplakov
for
.Ox
and ported to
.Nx
by
.An Lennart Augustsson .