AML has a complex grammar, and this makes runtime modifications
on an AML byte stream difficult. A solution is to parse the AML
bytecode and represent it in a tree data structure, henceforth
called the AML tree.
The AML tree is composite in the sense it has the following node
types:
- A 'Root node' that represents the root of the AML tree.
- An 'Object node' that contains the OP Code (AML Encoding).
- A 'Data node' that contains a data buffer.
The Root node contains the Definition block header (ACPI header)
and a Variable Argument list.
The Object node is composed of an array of Fixed Arguments and
a Variable Argument list.
Fixed arguments can be either Object Nodes or Data nodes. Their
placement (index) in the Fixed Argument array is defined by the
AML encoding of the enclosing Object Node.
Variable arguments can be Object nodes or Data nodes.
Following is a depiction of a typical AML tree:
(/) # Root Node
\
|-{(N1)->...} # Variable Argument list, N1 is
\ # an Object Node
\ /-i # Child of fixed argument b
\ /
|- [a][b][c][d] # Fixed Arguments
|- {(e)->(f)->(g)} # Variable Arguments
\
\-h # Child of variable argument e
Signed-off-by: Pierre Gondois <pierre.gondois@arm.com>
Signed-off-by: Sami Mujawar <sami.mujawar@arm.com>
Reviewed-by: Alexei Fedorov <Alexei.Fedorov@arm.com>
ASL is a source language for defining ACPI objects including
writing ACPI control methods. An ASL file is compiled using
an ASL compiler tool to generate ACPI Machine Language (AML).
This AML bytecode is processed by the ACPI AML interpreter
that runs as part of an Operating System (OS).
Both ASL and AML are declarative languages. Although they
are closely related they are different languages.
ASL statements declare objects. Each object has three parts,
two of which can be NULL:
Object := ObjectType FixedList VariableList
The AML grammar defines corresponding encodings that makes
up the AML byte stream.
This patch introduces the AML grammar definitions used by
AmlLib for encoding/decoding AML byte streams.
Signed-off-by: Pierre Gondois <pierre.gondois@arm.com>
Signed-off-by: Sami Mujawar <sami.mujawar@arm.com>
Reviewed-by: Alexei Fedorov <Alexei.Fedorov@arm.com>
Dynamic AML is a solution to generate Definition Block tables
at runtime. Dynamic AML provides the following techniques for
generating AML tables.
- AML Fixup
- AML Codegen
- AML Fixup + Codegen
AML fixup involves patching small sections of a template AML
code at runtime, while AML Codegen provides APIs to generate
small sections of AML code at runtime. A combination of
Fixup and Codegen can also be used.
AML has a complex grammar. To simplify the generation of
AML tables, Dynamic AML introduces AmlLib that provides a
rich set of APIs for parsing, traversing, fixup, codegen
and serialisation of AML byte code.
This patch introduces the definitions used by AmlLib.
Signed-off-by: Pierre Gondois <pierre.gondois@arm.com>
Signed-off-by: Sami Mujawar <sami.mujawar@arm.com>
Reviewed-by: Alexei Fedorov <Alexei.Fedorov@arm.com>
