mix.h

   1 /**
   2  * Opaque structure which corresponds to an instance of a mixer.
   3  *
   4  * A pointer to a structure of this type is returned by ->open().  This pointer
   5  * must be passed to most other methods of \ref struct mixer.
   6  */
   7 struct mixer_handle;
   8
   9 /**
  10  * Operations provided by each mixer plugin.
  11  */
  12 struct mixer {
  13         /** Called on startup, must fill in all other members. */
  14         void (*init)(struct mixer *self);
  15         /** Return a handle that can be passed to other methods. */
  16         int (*open)(const char *dev, struct mixer_handle **handle);
  17         /** Returns a string of all valid mixer channels. */
  18         char *(*get_channels)(struct mixer_handle *handle);
  19         /** Select the channel for subsequent get/set operations. */
  20         int (*set_channel)(struct mixer_handle *handle,
  21                 const char *mixer_channel);
  22         /** Return the (normalized) current value of the selected channel. */
  23         int (*get)(struct mixer_handle *handle);
  24         /** Change the value of the selected channel. */
  25         int (*set)(struct mixer_handle *handle, int val);
  26         /** Free all ressources associated with the given handle. */
  27         void (*close)(struct mixer_handle **handle);
  28 };