104 lines
3.3 KiB
Lua
104 lines
3.3 KiB
Lua
-- WirePlumber
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--
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-- Copyright © 2023 Collabora Ltd.
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-- @author George Kiagiadakis <george.kiagiadakis@collabora.com>
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--
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-- SPDX-License-Identifier: MIT
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--
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-- The script exposes a metadata object named "sm-objects" that clients can
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-- use to load objects into the WirePlumber daemon process. The objects are
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-- loaded as soon as the metadata is set and are destroyed when the metadata
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-- is cleared.
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--
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-- To load an object, a client needs to set a metadata entry with:
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--
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-- * subject:
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-- The ID of the owner of the object; you can use 0 here, but the
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-- idea is to be able to restrict which clients can change and/or
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-- delete these objects by using IDs of other objects appropriately
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--
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-- * key: "<UNIQUE-OBJECT-NAME>"
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-- This is the name that will be used to identify the object.
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-- If an object with the same name already exists, it will be destroyed.
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-- Note that the keys are unique per subject, so you can have multiple
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-- objects with the same name as long as they are owned by different subjects.
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--
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-- * type: "Spa:String:JSON"
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--
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-- * value: "{ type = <object-type>,
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-- name = <object-name>,
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-- args = { ...object arguments... } }"
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-- The object type can be one of the following:
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-- - "pw-module": loads a pipewire module: `name` and `args` are interpreted
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-- just like a module entry in pipewire.conf
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-- - "metadata": loads a metadata object with `metadata.name` = `name`
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-- and any additional properties provided in `args`
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--
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on_demand_objects = {}
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object_constructors = {
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["pw-module"] = LocalModule,
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["metadata"] = function (name, args)
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local m = ImplMetadata (name, args)
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m:activate (Features.ALL, function (m, e)
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if e then
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Log.warning ("failed to activate on-demand metadata `" .. name .. "`: " .. tostring (e))
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end
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end)
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return m
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end
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}
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function handle_metadata_changed (m, subject, key, type, value)
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-- destroy all objects when metadata is cleared
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if not key then
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on_demand_objects = {}
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return
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end
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local object_id = key .. "@" .. tostring(subject)
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-- destroy existing object instance, if needed
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if on_demand_objects[object_id] then
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Log.debug("destroy on-demand object: " .. object_id)
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on_demand_objects[object_id] = nil
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end
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if value then
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local json = Json.Raw(value)
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if not json:is_object() then
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Log.warning("loading '".. object_id .. "' failed: expected JSON object, got: '" .. value .. "'")
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return
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end
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local obj = json:parse(1)
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if not obj.type then
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Log.warning("loading '".. object_id .. "' failed: no object type specified")
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return
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end
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if not obj.name then
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Log.warning("loading '".. object_id .. "' failed: no object name specified")
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return
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end
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local constructor = object_constructors[obj.type]
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if not constructor then
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Log.warning("loading '".. object_id .. "' failed: unknown object type: " .. obj.type)
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return
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end
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Log.info("load on-demand object: " .. object_id .. " -> " .. obj.name)
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on_demand_objects[object_id] = constructor(obj.name, obj.args)
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end
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end
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objects_metadata = ImplMetadata ("sm-objects")
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objects_metadata:activate (Features.ALL, function (m, e)
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if e then
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Log.warning ("failed to activate the sm-objects metadata: " .. tostring (e))
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else
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m:connect("changed", handle_metadata_changed)
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end
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end)
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