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/* SPDX-License-Identifier: GPL-2.0 */
/** \file mix.h Mixer API for para_mixer. */
/**
* Opaque structure which corresponds to an instance of a mixer.
*
* A pointer to a structure of this type is returned by ->open(). This pointer
* must be passed to most other methods of \ref struct mixer.
*/
struct mixer_handle;
/**
* Operations provided by each mixer plugin.
*
* Each mixer plugin must define a non-static instance of this structure, with
* all pointers initialized to non-NULL values. No other symbols need to be
* exported.
*/
struct mixer {
/** Used to identify the mixer. */
const char * const name;
/** Return a handle that can be passed to other methods. */
int (*open)(const char *dev, struct mixer_handle **handle);
/** Returns a string of all valid mixer channels. */
char *(*get_channels)(struct mixer_handle *handle);
/** Select the channel for subsequent get/set operations. */
int (*set_channel)(struct mixer_handle *handle,
const char *mixer_channel);
/** Return the (normalized) current value of the selected channel. */
int (*get)(const struct mixer_handle *handle);
/** Change the value of the selected channel. */
int (*set)(struct mixer_handle *handle, int val);
/** Free all resources associated with the given handle. */
void (*close)(struct mixer_handle *handle);
};
/*
* The alsa_mixer structure is declared even on *BSD where the alsa API is
* unsupported. This does not hurt, and it avoids ifdefs.
*/
extern const struct mixer alsa_mixer, oss_mixer;
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