system/dev/audio/usb-audio/usb-audio-path.h

// Copyright 2018 The Fuchsia Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#pragma once

#include <fbl/macros.h>
#include <fbl/intrusive_double_list.h>
#include <fbl/unique_ptr.h>

#include <utility>

#include "usb-audio.h"
#include "usb-audio-units.h"

namespace audio {
namespace usb {

class UsbAudioControlInterface;

// A small container class used by the audio control interface for describing a
// path through the unit/terminal graph from host to pin (or vice-versa)
class AudioPath : public fbl::DoublyLinkedListable<fbl::unique_ptr<AudioPath>> {
  public:
    Direction direction() const { return direction_; }
    const Terminal& stream_terminal() const {
        // If we do not have a stashed pointer to our terminal yet, then someone
        // is calling this accessor before Setup completed successfully.  This
        // should never happen.
        ZX_DEBUG_ASSERT(stream_terminal_ != nullptr);
        return *stream_terminal_;
    }

    bool  has_gain() const { return feature_unit_ && feature_unit_->has_vol(); }
    bool  has_agc()  const { return feature_unit_ && feature_unit_->has_agc(); }
    bool  has_mute() const { return feature_unit_ && feature_unit_->has_mute(); }
    float cur_gain() const { return feature_unit_ ? feature_unit_->vol_cur_db() : 0.0f; }
    float min_gain() const { return feature_unit_ ? feature_unit_->vol_min_db() : 0.0f; }
    float max_gain() const { return feature_unit_ ? feature_unit_->vol_max_db() : 0.0f; }
    float gain_res() const { return feature_unit_ ? feature_unit_->vol_res_db() : 0.0f; }
    bool  cur_agc()  const { return feature_unit_ ? feature_unit_->agc_cur() : false; }
    bool  cur_mute() const { return feature_unit_ ? feature_unit_->mute_cur() : false; }

    float SetGain(const usb_protocol_t& proto, float db) {
        return feature_unit_ ? feature_unit_->SetVol(proto, db) : 0.0f;
    }

    bool SetMute(const usb_protocol_t& proto, bool mute) {
        return feature_unit_ ? feature_unit_->SetMute(proto, mute) : false;
    }

    bool SetAgc(const usb_protocol_t& proto, bool enabled) {
        return feature_unit_ ? feature_unit_->SetAgc(proto, enabled) : false;
    }

  private:
    friend class fbl::unique_ptr<AudioPath>;
    friend class UsbAudioControlInterface;

    // Methods use by the audio control interface class to build audio paths
    // during its walk of the unit/terminal graph.  Basically, the control
    // interface class calls...
    //
    // 1) 'Create' when it finds what looks like a valid path during its recursive
    //    walk of the graph.
    // 2) 'AddUnit' as it unwinds from the walk in order to store references
    //    which form the path in the proper order inside of the path.
    // 3) 'Setup' when it is finished in order to sanity check the path and to
    //    stash pointers to important elements, such as the stream terminal
    //    node and the feature unit node (if found).
    //
    static fbl::unique_ptr<AudioPath> Create(uint32_t unit_count);
    void AddUnit(uint32_t ndx, fbl::RefPtr<AudioUnit> unit);
    zx_status_t Setup(const usb_protocol_t& proto);

     AudioPath(fbl::unique_ptr<fbl::RefPtr<AudioUnit>[]> units, uint32_t unit_count)
         : units_(std::move(units)), unit_count_(unit_count) {}
    ~AudioPath() {}

    DISALLOW_COPY_ASSIGN_AND_MOVE(AudioPath);

    const fbl::unique_ptr<fbl::RefPtr<AudioUnit>[]> units_;
    const uint32_t unit_count_;
    Direction direction_ = Direction::Unknown;

    // Note: Strictly speaking, these cached references do not have to be
    // RefPtrs.  In theory, the members of units_ should always outlive these
    // cache references.   This said, the cost of holding an extra reference on
    // the objects is basically zero, and storing the pointers internally as
    // RefPtr<>s makes it easy to know that this is safe from a lifecycle
    // perspective, if perhaps a tiny bit paranoid.
    fbl::RefPtr<const Terminal> stream_terminal_;
    fbl::RefPtr<FeatureUnit> feature_unit_;
};

}  // namespace usb
}  // namespace audio