xref: /freebsd/share/man/man9/OF_node_from_xref.9 (revision fa9896e082a1046ff4fbc75fcba4d18d1f2efc19)

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.Dd April 9, 2018
.Dt OF_NODE_FROM_XREF 9
.Os
.Sh NAME
.Nm OF_node_from_xref ,
.Nm OF_xref_from_node
.Nd convert between kernel phandle and effective phandle
.Sh SYNOPSIS
.In dev/ofw/ofw_bus.h
.In dev/ofw/ofw_bus_subr.h
.Ft phandle_t
.Fn OF_node_from_xref "phandle_t xref"
.Ft phandle_t
.Fn OF_xref_from_node "phandle_t node"
.Sh DESCRIPTION
Some OpenFirmware implementations (FDT, IBM) have a concept
of effective phandle or xrefs.
They are used to cross-reference device tree nodes.
For instance, a framebuffer controller may refer to a GPIO
controller and pin that controls the backlight.
In this example, the GPIO node would have a cell (32-bit integer)
property with a reserved name like "phandle" or "linux,phandle"
whose value uniquely identifies the node.
The actual name depends on the implementation.
The framebuffer node would have a property with the name
described by device bindings (device-specific set of properties).
It can be a cell property or a combined property with one part
of it being a cell.
The value of the framebuffer node's property would be the same
as the value of the GPIO "phandle" property so it can be said
that the framebuffer node refers to the GPIO node.
The kernel uses internal logic to assign unique identifiers
to the device tree nodes, and these values do not match
the values of "phandle" properties.
.Fn OF_node_from_xref
and
.Fn OF_xref_from_node
are used to perform conversion between these two kinds of node
identifiers.
.Pp
.Fn OF_node_from_xref
returns the kernel phandle for the effective phandle
.Fa xref .
If one cannot be found or the OpenFirmware implementation
does not support effective phandles, the function returns
the input value.
.Pp
.Fn OF_xref_from_xref
returns the effective phandle for the kernel phandle
.Fa xref .
If one cannot be found or the OpenFirmware implementation
does not support effective phandles, the function returns
the input value.
.Sh EXAMPLES
.Bd -literal
    phandle_t panelnode, panelxref;
    char *model;

    if (OF_getencprop(node, "lcd-panel", &panelxref) <= 0)
        return;

    panelnode = OF_node_from_xref(panelxref);
    if (OF_getprop_alloc(hdminode, "model", (void **)&model) <= 0)
        return;
.Ed
.Sh SEE ALSO
.Xr OF_device_from_xref 9 ,
.Xr OF_device_register_xref 9
.Sh AUTHORS
.An -nosplit
This manual page was written by
.An Oleksandr Tymoshenko Aq Mt gonzo@FreeBSD.org .