This patch adds support for pre-processing the Topology2.0.
The '-p' switch add pre-processing support during compilation
and the '-P' switch is for converting the Topology2.0
configuration file into the existing syntax.
Topology2.0 is a high level keyword extension on top of the existing ALSA
conf topology format designed to:
1) Simplify the ALSA conf topology definitions by providing high level
"classes" so topology designers need to write less config for common
object definitions.
2) Allow simple reuse of objects. Define once and reuse (like M4) with
the ability to alter objects configuration attributes from defaults.
3) Allow data type and value verification. This is not done today and
frequently crops up in FW bug reports.
Common Topology Classes
-----------------------
Topology today has some common classes that are often reused throughout
with slightly altered configurations. i.e. widgets (components),
pipelines, dais and controls.
Topology2.0 introduces the high level concept of reusable "class" like
definition for that can be used to create topology objects.
Common Topology Attributes
--------------------------
Topology defines a lot of attributes per object with different types
and constraints. Today there is no easy way to validate type or
constraints and this can lead to many hard to find problems in FW at
runtime.
A new keyword "DefineAttribute" has been added to define attribute
constraints such as min value, max value, enum_values etc. This
then allows alsatplg to validate each topology object attribute.
Topology Classes define the list of attributes that they use and
whether the attribute is mandatory, can be overridden by parent users
or is immutable. This also helps alsatplg emit the appropriate errors
for attribute misuse.
Class constructor attributes
----------------------------
Some attributes in the class definition are declared as constructor
attributes and these will be used to construct the name of the object.
For ex: for the host widget, the index and direction are constructor
attributes and the name for the widget is derived as follows:
host.1.playback or host.2.capture etc.
Attribute Inheritance:
----------------------
One of the key features of Topology2.0 is how the attribute values are
propagated from a parent object to a child object. For ex: a pipeline
object can pass down the pipeline_id attribute to all its widgets.
Inheritance is implicit when an object and its embedded child objects
have matching names for a attribute/argument. Attribute values
set explicitly in an object instance always has precedence over
the values inherited from the parent object.
Signed-off-by: Ranjani Sridharan <ranjani.sridharan@linux.intel.com>
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Signed-off-by: Jaroslav Kysela <perex@perex.cz>
