.\"	$OpenBSD: aml_evalnode.9,v 1.10 2014/01/21 03:15:46 schwarze Exp $
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.\" Copyright (c) 2007 Michael Knudsen <mk@openbsd.org>
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.Dd $Mdocdate: January 21 2014 $
.Dt AML_EVALNODE 9
.Os
.Sh NAME
.Nm aml_evalnode ,
.Nm aml_evalname ,
.Nm aml_find_node ,
.Nm aml_freevalue ,
.Nm aml_val2int
.Nd AML API
.Sh SYNOPSIS
.In dev/acpi/acpireg.h
.In dev/acpi/acpivar.h
.In dev/acpi/acpidev.h
.In dev/acpi/amltypes.h
.In dev/acpi/dsdt.h
.Ft int
.Fn "aml_evalnode" "struct acpi_softc *sc" "struct aml_node *node" \
"int argc" "struct aml_value *argv" "struct aml_value *res"
.Ft int
.Fn "aml_evalname" "struct acpi_softc *sc" "struct aml_node *parent" \
"const char *name" "int argc" "struct aml_value *argv" \
"struct aml_value *res"
.Ft int
.Fn "aml_find_node" "struct aml_node *node" "const char *name" \
"int (*cbproc)(struct aml_node *, void *arg)" "void *arg"
.Ft void
.Fn "aml_freevalue" "struct aml_value *val"
.Ft int64_t
.Fn "aml_val2int" "struct aml_value *rval"
.Sh DESCRIPTION
The AML API handles decoding and evaluation of the AML
code embedded in a machine's ACPI tables.
This code is used to implement configuration and control mechanisms for
machines.
.Pp
.Fn aml_evalnode
evaluates the AML node
.Fa node
located in the ACPI table specified by
.Fa sc .
Parameters may be passed using the
.Fa argv
parameters with the parameter
.Fa argc
specifying the number of parameters passed.
If there are no arguments,
a value of 0 is used for
.Fa argc
and
.Fa argv
should be
.Dv NULL .
If evaluating the node produces any result, for example a string with a device
name reference, this result is stored in the
.Fa res
parameter unless it is
.Dv NULL .
.Fa res
is cleared before storing the result.
If
.Fa node
does not exist,
.Fn aml_evalnode
returns
.Dv ACPI_E_BADVALUE ,
otherwise it returns 0.
.Pp
.Fn aml_evalname
is similar to
.Fn aml_evalnode
but differs in that it searches for a subnode of
.Fa parent
with the name
.Fa name .
If such a node is found, it is evaluated using
.Fn aml_evalnode ,
passing whatever parameters were passed to itself.
.Fn aml_evalname
returns the return value of
.Fn aml_evalnode .
.Pp
.Fn aml_find_node
is used to find all subnodes of
.Fa parent
with a name of
.Fa name  .
For each node found, the function specified as the
.Fa cbproc
parameter is called with the node and
.Fa arg
as the first and second parameters, respectively.
The function specified as the
.Fa cbproc
parameter returns a value that specifies if the tree walk
should be terminated (!0) or continued (0) with the children.
.Fn aml_find_node
always returns 0.
.Pp
.Fn aml_freevalue
is used to free up the result returned from
.Fn aml_evalnode
or the other AML evaluation functions.
Note that no attempt is made to free the
.Vt struct aml_value
itself so it is safe to allocate this on the stack.
Also, calling
.Fn aml_freevalue
with a parameter of
.Dv NULL
is not an error.
.Pp
.Fn aml_val2int
is used to convert the
.Vt struct aml_value
pointed to by the
.Fa rval
parameter to a signed 64-bit integer value.
Multiple types exist for
.Vt struct aml_value ,
and the conversion value depends on the type
of the value object as follows.
For objects of type
.Dv AML_OBJTYPE_INTEGER
and
.Dv AML_OBJTYPE_STATICINT ,
the return value is simply the integer value stored in the object.
For objects of type
.Dv AML_OBJTYPE_BUFFER ,
the return value is the integer interpretation of the buffer contents.
For objects of type
.Dv AML_OBJTYPE_STRING ,
the return value is the integer value represented as a string in base 10
or, if prefixed by
.Dq 0x ,
in base 16.
If
.Fa rval
is
.Dv NULL
or not of one of the types mentioned above,
.Fn aml_val2int
returns 0.
.Sh EXAMPLES
Using
.Fn aml_evalname
to invoke the
.Dq _STA
method on a node
.Fa node
should be done like the following:
.Bd -literal -offset indent
struct acpi_softc	*sc
struct aml_node		*node;
struct aml_value	res;

if (aml_evalname(sc->sc_acpi, node, "_STA", 0, NULL, &res) != 0) {
	dnprintf(10, "%s: no _STA\en", DEVNAME(sc));
	return;
}
.Ed
.Pp
Using the
.Vt struct aml_value
obtained from the
.Dq _STA
call to determine if the device is a battery is done as follows:
.Bd -literal -offset indent
if ((aml_val2int(&res) & STA_BATTERY) == 0) {
	dnprintf(10, %s: no battery present\en", DEVNAME(sc));
	return;
.Ed
.Pp
Finally, when the result stored in
.Fa res
is no longer needed, free it using
.Fn aml_freevalue :
.Bd -literal -offset indent
aml_freevalue(&res);
.Ed
.Sh SEE ALSO
.Xr acpi 4 ,
.Xr acpidump 8
.Sh HISTORY
The AML API was written by
.An Jordan Hargrave Aq Mt jordan@openbsd.org .