mix.h

   1 /*
   2  * Copyright (C) 2012-2014 Andre Noll <maan@systemlinux.org>
   3  *
   4  * Licensed under the GPL v2. For licencing details see COPYING.
   5  */
   6
   7 /** \file mix.h Mixer API (used by para_fade). */
   8
   9 /**
  10  * Opaque structure which corresponds to an instance of a mixer.
  11  *
  12  * A pointer to a structure of this type is returned by ->open().  This pointer
  13  * must be passed to most other methods of \ref struct mixer.
  14  */
  15 struct mixer_handle;
  16
  17 /**
  18  * Operations provided by each mixer plugin.
  19  */
  20 struct mixer {
  21         /** Called on startup, must fill in all other members. */
  22         void (*init)(struct mixer *self);
  23         /** Return a handle that can be passed to other methods. */
  24         int (*open)(const char *dev, struct mixer_handle **handle);
  25         /** Returns a string of all valid mixer channels. */
  26         char *(*get_channels)(struct mixer_handle *handle);
  27         /** Select the channel for subsequent get/set operations. */
  28         int (*set_channel)(struct mixer_handle *handle,
  29                 const char *mixer_channel);
  30         /** Return the (normalized) current value of the selected channel. */
  31         int (*get)(struct mixer_handle *handle);
  32         /** Change the value of the selected channel. */
  33         int (*set)(struct mixer_handle *handle, int val);
  34         /** Free all ressources associated with the given handle. */
  35         void (*close)(struct mixer_handle **handle);
  36 };