OF_getprop.9

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.Dd June 23, 2018
.Dt OF_GETPROP 9
.Os
.Sh NAME
.Nm OF_getprop ,
.Nm OF_getproplen ,
.Nm OF_getencprop ,
.Nm OF_hasprop ,
.Nm OF_searchprop ,
.Nm OF_searchencprop ,
.Nm OF_getprop_alloc ,
.Nm OF_getencprop_alloc ,
.Nm OF_getprop_alloc_multi ,
.Nm OF_getencprop_alloc_multi ,
.Nm OF_prop_free ,
.Nm OF_nextprop ,
.Nm OF_setprop
.Nd access properties of device tree node
.Sh SYNOPSIS
.In dev/ofw/ofw_bus.h
.In dev/ofw/ofw_bus_subr.h
.Ft ssize_t
.Fn OF_getproplen "phandle_t node" "const char *propname"
.Ft ssize_t
.Fn OF_getprop "phandle_t node" "const char *propname" \
"void *buf" "size_t len"
.Ft ssize_t
.Fn OF_getencprop "phandle_t node" "const char *prop" \
"pcell_t *buf" "size_t len"
.Ft int
.Fn OF_hasprop "phandle_t node" "const char *propname"
.Ft ssize_t
.Fn OF_searchprop "phandle_t node" "const char *propname" \
"void *buf" "size_t len"
.Ft ssize_t
.Fn OF_searchencprop "phandle_t node" "const char *propname" \
"pcell_t *buf" "size_t len"
.Ft ssize_t
.Fn OF_getprop_alloc "phandle_t node" "const char *propname" \
"void **buf"
.Ft ssize_t
.Fn OF_getencprop_alloc "phandle_t node" "const char *propname" \
"pcell_t **buf"
.Ft ssize_t
.Fn OF_getprop_alloc_multi "phandle_t node" "const char *propname" \
"int elsz" "void **buf"
.Ft ssize_t
.Fn OF_getencprop_alloc_multi "phandle_t node" "const char *propname" \
"int elsz" "pcell_t **buf"
.Ft void
.Fn OF_prop_free "void *buf"
.Ft int
.Fn OF_nextprop "phandle_t node" "const char *propname" \
"char *buf" "size_t len"
.Ft int
.Fn OF_setprop "phandle_t node" "const char *propname" \
"const void *buf" "size_t len"
.Sh DESCRIPTION
Device nodes can have associated properties.
Properties consist of a name and a value.
A name is a human-readable string from 1 to 31 characters long.
A value is an array of zero or more bytes that encode certain
information.
The meaning of that bytes depends on how drivers interpret them.
Properties can encode byte arrays, text strings, unsigned 32-bit
values or any combination of these types.
.Pp
Property with a zero-length value usually represents boolean
information.
If the property is present, it signifies true, otherwise false.
.Pp
A byte array is encoded as a sequence of bytes and represents
values like MAC addresses.
.Pp
A text string is a sequence of n printable characters.
It is encoded as a byte array of length n + 1 bytes with
characters represented as bytes plus a terminating null character.
.Pp
Unsigned 32-bit values, also sometimes called cells, are
encoded as a sequence of 4 bytes in big-endian order.
.Pp
.Fn OF_getproplen
returns either the length of the value associated with the property
.Fa propname
in the node identified by
.Fa node ,
or 0 if the property exists but has no associated value.
If
.Fa propname
does not exist, -1 is returned.
.Pp
.Fn OF_getprop
copies a maximum of
.Fa len
bytes from the value associated with the property
.Fa propname
of the device node
.Fa node
into the memory specified by
.Fa buf .
Returns the actual size of the value or -1 if the
property does not exist.
.Pp
.Fn OF_getencprop
copies a maximum of
.Fa len
bytes into memory specified by
.Fa buf ,
then converts cell values from big-endian to host byte order.
Returns the actual size of the value in bytes, or -1
if the property does not exist.
.Fa len
must be a multiple of 4.
.Pp
.Fn OF_hasprop
returns 1 if the device node
.Fa node
has a property specified by
.Fa propname ,
and zero if the property does not exist.
.Pp
.Fn OF_searchprop
recursively looks for the property specified by
.Fa propname
starting with the device node
.Fa node
followed by the parent node and up to the root node.
If the property is found, the function copies a maximum of
.Fa len
bytes of the value associated with the property
into the memory specified by
.Fa buf .
Returns the actual size in bytes of the value,
or -1 if the property does not exist.
.Pp
.Fn OF_searchencprop
recursively looks for the property specified by
.Fa propname
starting with the device node
.Fa node
followed by the parent node and up to the root node.
If the property is found, the function copies a maximum of
.Fa len
bytes of the value associated with the property
into the memory specified by
.Fa buf ,
then converts cell values from big-endian to host byte order.
Returns the actual size in bytes of the value,
or -1 if the property does not exist.
.Pp
.Fn OF_getprop_alloc
allocates memory large enough to hold the
value associated with the property
.Fa propname
of the device node
.Fa node
and copies the value into the newly allocated memory region.
Returns the actual size of the value and stores
the address of the allocated memory in
.Fa *buf .
If the property has a zero-sized value
.Fa *buf
is set NULL.
Returns -1 if the property does not exist or
memory allocation failed.
Allocated memory should be released when no longer required
by calling
.Fn OF_prop_free .
The function might sleep when allocating memory.
.Pp
.Fn OF_getencprop_alloc
allocates enough memory to hold the
value associated with the property
.Fa propname
of the device node
.Fa node ,
copies the value into the newly allocated memory region, and
then converts cell values from big-endian to host byte
order.
The actual size of the value is returned and the
address of allocated memory is stored in
.Fa *buf .
If the property has zero-length value,
.Fa *buf
is set to NULL.
Returns -1 if the property does not exist or
memory allocation failed or the size of the value is not
divisible by a cell size (4 bytes).
Allocated memory should be released when no longer required
by calling
.Fn OF_prop_free .
The function might sleep when allocating memory.
.Pp
.Fn OF_getprop_alloc_multi
allocates memory large enough to hold the
value associated with the property
.Fa propname
of the device node
.Fa node
and copies the value into the newly allocated memory region.
The value is expected to be an array of zero or more elements
.Fa elsz
bytes long.
Returns the number of elements in the value and stores
the address of the allocated memory in
.Fa *buf .
If the property has a zero-sized value
.Fa *buf
is set NULL.
Returns -1 if the property does not exist or
memory allocation failed or the size of the value is not
divisible by
.Fa elsz .
Allocated memory should be released when no longer required
by calling
.Fn OF_prop_free .
The function might sleep when allocating memory.
.Pp
.Fn OF_getencprop_alloc_multi
allocates memory large enough to hold the
value associated with the property
.Fa propname
of the device node
.Fa node
and copies the value into the newly allocated memory region, and
then converts cell values from big-endian to host byte
order.
The value is expected to be an array of zero or more elements
.Fa elsz
bytes long.
Returns the number of elements in the value and stores
the address of the allocated memory in
.Fa *buf .
If the property has a zero-sized value
.Fa *buf
is set NULL.
Returns -1 if the property does not exist or
memory allocation failed or the size of the value is not
divisible by
.Fa elsz .
Allocated memory should be released when no longer required
by calling
.Fn OF_prop_free .
The function might sleep when allocating memory.
.Pp
.Fn OF_prop_free
releases memory at
.Fa buf
that was allocated by
.Fn OF_getprop_alloc ,
.Fn OF_getencprop_alloc ,
.Fn OF_getprop_alloc_multi ,
.Fn OF_getencprop_alloc_multi .
.Pp
.Fn OF_nextprop
copies a maximum of
.Fa size
bytes of the name of the property following the
.Fa propname
property into
.Fa buf .
If
.Fa propname
is NULL, the function copies the name of the first property of the
device node
.Fa node .
.Fn OF_nextprop
returns -1 if
.Fa propname
is invalid or there is an internal error, 0 if there are no more
properties after
.Fa propname ,
or 1 otherwise.
.Pp
.Fn OF_setprop
sets the value of the property
.Fa propname
in the device node
.Fa node
to the value beginning at the address specified by
.Fa buf
and running for
.Fa len
bytes.
If the property does not exist, the function tries to create
it.
.Fn OF_setprop
returns the actual size of the new value, or -1 if the
property value cannot be changed or the new property
cannot be created.
.Sh EXAMPLES
.Bd -literal
    phandle_t node;
    phandle_t hdmixref, hdminode;
    device_t hdmi;
    uint8_t mac[6];
    char *model;

    /*
     * Get a byte array property
     */
    if (OF_getprop(node, "eth,hwaddr", mac, sizeof(mac)) != sizeof(mac))
        return;

    /*
     * Get internal node reference and device associated with it
     */
    if (OF_getencprop(node, "hdmi", &hdmixref) <= 0)
        return;
    hdmi = OF_device_from_xref(hdmixref);

    /*
     * Get string value of model property of HDMI framer node
     */
    hdminode = OF_node_from_xref(hdmixref);
    if (OF_getprop_alloc(hdminode, "model", (void **)&model) <= 0)
        return;
.Ed
.Sh SEE ALSO
.Xr OF_device_from_xref 9 ,
.Xr OF_node_from_xref 9
.Sh AUTHORS
.An -nosplit
This manual page was written by
.An Oleksandr Tymoshenko Aq Mt gonzo@FreeBSD.org .