xref: /freebsd/share/man/man4/openfirm.4 (revision 97759ccc715c4b365432c16d763c50eecfcb1100)

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.Dd January 16, 2021
.Dt OPENFIRM 4
.Os
.Sh NAME
.Nm openfirm
.Nd "Open Firmware interface"
.Sh SYNOPSIS
.In sys/types.h
.In sys/ioctl.h
.In dev/ofw/openfirmio.h
.Sh DESCRIPTION
The
.Pa /dev/openfirm
device is an interface to the
.Tn Open Firmware
device tree.
This interface is highly stylized.
It uses
.Xr ioctl 2
calls for all operations.
These calls refer to the nodes in the
.Tn Open Firmware
device tree.
The nodes are represented by package handles,
which are simply integer values describing data areas.
Occasionally a package handle of 0 may be used or returned instead,
as described below.
.Pp
The calls that only take and/or return the package handle of a node
use a pointer to a
.Vt phandle_t
for this purpose.
The others use a pointer to a
.Vt "struct ofiocdesc"
descriptor,
which has the following definition:
.Bd -literal
struct ofiocdesc {
	phandle_t	of_nodeid;
	int		of_namelen;
	const char	*of_name;
	int		of_buflen;
	char		*of_buf;
};
.Ed
.Pp
The
.Va of_nodeid
member is the package handle of the node that is passed in or returned.
Strings are passed in via the
.Va of_name
member of
.Va of_namelen
length.
The maximum accepted length of
.Va of_name
is
.Dv OFIOCMAXNAME .
The
.Va of_buf
member is used to return strings except for the
.Dv OFIOCSET
call where it is also used to pass in a string.
In the latter case the maximum accepted length of
.Va of_buf
is
.Dv OFIOCMAXVALUE .
Generally,
.Va of_buf
works in a value-result fashion.
At entry to the
.Xr ioctl 2
call,
.Va of_buflen
is expected to reflect the buffer size.
On return,
.Va of_buflen
is updated to reflect the buffer contents.
.Pp
The following
.Xr ioctl 2
calls are supported:
.Bl -tag -width ".Dv OFIOCGETOPTNODE"
.It Dv OFIOCGETOPTNODE
Uses a
.Vt phandle_t .
Takes nothing and returns the package handle of the
.Pa /options
node.
.It Dv OFIOCGETNEXT
Uses a
.Vt phandle_t .
Takes the package handle of a node and returns the package handle of the next
node in the
.Tn Open Firmware
device tree.
The node following the last node has a package handle of 0.
The node following the node with the package handle of 0 is the first node.
.It Dv OFIOCGETCHILD
Uses a
.Vt phandle_t .
Takes the package handle of a node and returns the package handle of the first
child of that node.
This child may have siblings.
These can be determined by using
.Dv OFIOCGETNEXT .
If the node does not have a child,
a package handle of 0 is returned.
.It Dv OFIOCGET
Uses a
.Vt "struct ofiocdesc" .
Takes the package handle of a node and the name of a property.
Returns the property value and its length.
If no such property is associated with that node,
the length of the value is set to \-1.
If the named property exists but has no value,
the length of the value is set to 0.
.It Dv OFIOCGETPROPLEN
Uses a
.Vt "struct ofiocdesc" .
Takes the package handle of a node and the name of a property.
Returns the length of the property value.
This call is the same as
.Dv OFIOCGET
except that only the length of the property value is returned.
It can be used to determine whether a node has a particular property or whether
a property has a value without the need to provide memory for storing the value.
.It Dv OFIOCSET
Uses a
.Vt "struct ofiocdesc" .
Takes the package handle of a node,
the name of a property and a property value.
Returns the property value and the length that actually have been written.
The
.Tn Open Firmware
may choose to truncate the value if it is too long or write a valid value
instead if the given value is invalid for the particular property.
Therefore the returned value should be checked.
The
.Tn Open Firmware
may also completely refuse to write the given value to the property.
In this case
.Er EINVAL
is returned.
.It Dv OFIOCNEXTPROP
Uses a
.Vt "struct ofiocdesc" .
Takes the package handle of a node and the name of a property.
Returns the name and the length of the next property of the node.
If the property referenced by the given name is the last property of the node,
.Er ENOENT
is returned.
.It Dv OFIOCFINDDEVICE
Uses a
.Vt "struct ofiocdesc" .
Takes the name or alias name of a device node.
Returns package handle of the node.
If no matching node is found,
.Er ENOENT
is returned.
.El
.Sh FILES
.Bl -tag -width ".Pa /dev/openfirm"
.It Pa /dev/openfirm
Open Firmware interface node
.El
.Sh DIAGNOSTICS
The following may result in rejection of an operation:
.Bl -tag -width Er
.It Bq Er EBADF
The requested operation requires permissions not specified at the call to
.Fn open .
.It Bq Er EINVAL
The given package handle is not 0 and does not correspond to any valid node,
or the given package handle is 0 where 0 is not allowed.
.It Bq Er ENAMETOOLONG
The given name or value exceeds the maximum allowed length of
.Dv OFIOCMAXNAME
and
.Dv OFIOCMAXVALUE
bytes respectively.
.El
.Sh SEE ALSO
.Xr ioctl 2 ,
.Xr ofwdump 8
.Rs
.%Q "IEEE Standards Organization"
.%B "IEEE Std 1275-1994:"
.%B "IEEE Standard for Boot Firmware (Initialization Configuration) Firmware:"
.%B Core Requirements and Practices"
.%O ISBN 1-55937-426-8
.Re
.Sh HISTORY
The
.Nm
interface first appeared in
.Nx 1.6 .
The first
.Fx
version to include it was
.Fx 5.0 .
.Sh AUTHORS
.An -nosplit
The
.Nm
interface was ported to
.Fx
by
.An Thomas Moestl Aq Mt tmm@FreeBSD.org .
This manual page was written by
.An Marius Strobl Aq Mt marius@FreeBSD.org
based on the
.Ox
manual page for
.Xr openprom 4 .
.Sh CAVEATS
Due to limitations within
.Tn Open Firmware
itself,
these functions run at elevated priority and may adversely affect system
performance.
.Pp
For at least the
.Pa /options
node the property value passed in to the
.Dv OFIOCSET
call has to be null-terminated and the value length passed in has to include
the terminating
.Ql \e0 .
However, as with the
.Dv OFIOCGET
call,
the returned value length does not include the terminating
.Ql \e0 .