The first purpose is for applications that wish to learn about the list of audio devices on the system, so that they can select (or provide for users to select) an appropriate audio device. The /dev/mixer pseudo-device provides interfaces to enumerate all of the audio devices on the system.

The second purpose is for mixer panel type applications which need to control master settings for the audio hardware in the system, such as gain levels, balance, port functionality, and other device features.

The argument is a pointer to an integer, which retrieves the version of the OSS API used. The value is encoded with the major version (currently 4) encoded in the most significant 16 bits, and a minor version encoded in the lower 16 bits.

The argument is a pointer to an oss_sysinfo structure, which has the following definition:

typedef struct oss_sysinfo {
 char product[32]; /* E.g. SunOS Audio */
 char version[32]; /* E.g. 4.0a */
 int versionnum; /* See OSS_GETVERSION */
 char options[128]; /* NOT SUPPORTED */

 int numaudios; /* # of audio/dsp devices */
 int openedaudio[8]; /* Reserved, always 0 */

 int numsynths; /* NOT SUPPORTED, always 0 */
 int nummidis; /* NOT SUPPORTED, always 0 */
 int numtimers; /* NOT SUPPORTED, always 0 */
 int nummixers; /* # of mixer devices */

 int openedmidi[8]; /* Mask of midi devices are 
 busy */
 int numcards; /* Number of sound cards in 
 the system */
 int numaudioengines; /* Number of audio engines in 
 the system */
 char license[16]; /* E.g. "GPL" or "CDDL" */
 char revision_info[256]; /* Reserved */
 int filler[172]; /* Reserved */
} oss_sysinfo;

The argument is a pointer to an oss_audioinfo structure, which has the following structure:

typedef struct oss_audioinfo {
 int dev; /* Device to query */
 char name[64]; /* Human readable name */
 int busy; /* reserved */
 int pid; /* reserved */
 int caps; /* PCM_CAP_INPUT, PCM_CAP_OUTPUT */
 int iformats; /* Supported input formats */
 int oformats; /* Supported output formats */
 int magic; /* reserved */
 char cmd[64]; /* reserved */
 int card_number;
 int port_number; /* reserved */
 int mixer_dev;
 int legacy_device; /* Obsolete field. 
 Replaced by devnode */
 int enabled; /* reserved */
 int flags; /* reserved */
 int min_rate; /* Minimum sample rate */
 int max_rate; /* Maximum sample rate */
 int min_channels; /* Minimum number 
 of channels */
 int max_channels; /* Maximum number 
 of channels */
 int binding; /* reserved */
 int rate_source; /* reserved */
 char handle[32]; /* reserved */
 unsigned int nrates; /* reserved */
 unsigned int rates[20]; /* reserved */
 char song_name[64]; /* reserved */
 char label[16]; /* reserved */
 int latency; /* reserved */
 char devnode[32]; /* Device special file 
 name (absolute path) */
 int next_play_engine; /* reserved */
 int next_rec_engine; /* reserved */
 int filler[184]; /* reserved */
} oss_audioinfo;

The argument is a pointer to a struct oss_card_info, which has the following definition:

typedef struct oss_card_info {
int card;
 char shortname[16];
 char longname[128];
 int flags;/* reserved */
 char hw_info[400];
 int intr_count;/* reserved */
 int ack_count;/* reserved */
 int filler[154];
} oss_card_info;

The argument is a pointer to a struct oss_mixer_info, which has the following definition:

typedef struct oss_mixerinfo {
 int dev;
 char id[16];/* Reserved */
 char name[32];
 int modify_counter;
 int card_number;
 int port_number;/* Reserved */
 char handle[32];/* Reserved */
 int magic;/* Reserved */
 int enabled;/* Reserved */
 int caps;/* Reserved */
 int flags;/* Reserved */
 int nrext;
 int priority;
 char devnode[32];/* Device special file name 
 (absolute path) */
 int legacy_device;/* Reserved */
 int filler[245];/* Reserved */
} oss_mixerinfo;

The argument is a pointer to an integer, which receives the number of mixer devices in the system. Each can be queried by using its number with the SNDCTL_MIXERINFO ioctl. The same information is available using the SNDCTL_SYSINFO ioctl.

The argument is a pointer to an integer. On entry, the integer should contain the special value -1. On return the argument receives the number of mixer extensions (or mixer controls) supported by the mixer device. More details about each extension can be obtained by SNDCTL_MIX_EXTINFO ioctl.

The argument is a pointer to an oss_mixext structure which is defined as follows:

typedef struct oss_mixext {
 int dev; /* Mixer device number */
 int ctrl; /* Extension number */
 int type; /* Entry type */
 int maxvalue;
 int minvalue;
 int flags;
 char id[16]; /* Mnemonic ID (internal use) */
 int parent; /* Entry# of parent 
 (-1 if root) */
 int dummy; /* NOT SUPPORTED */
 int timestamp;
 char data[64]; /* Reserved */
 unsigned char enum_present[32]; /* Mask 
 of allowed 
 enum 
 values */
 int control_no; /* Reserved */
 unsigned int desc; /* NOT SUPPORTED */
 char extname[32];
 int update_counter;
 int filler[7]; /* Reserved */
} oss_mixext;

MIXT_DEVROOT Root node for extension tree
MIXT_GROUP Logical grouping of controls
MXIT_ONOFF Boolean value, 0 = off, 1 = on.
MIXT_ENUM Enumerated value, 0 to maxvalue.
MIXT_MONOSLIDER Monophonic slider, 0 to 255.
MIXT_STEREOSLIDER Stereophonic slider, 0 to 255 
 (encoded as
 lower two bytes in value.)
MIXT_MARKER Place holder, can ignore.

MIXF_READABLE Extension's value is readable.
MIXF_WRITEABLE Extension's value is modifiable.
MIXF_POLL Extension can self-update.
MIXF_PCMVOL Extension is for master 
 PCM playback volume.
MIXF_MAINVOL Extension is for a typical 
 analog volume
MIXF_RECVOL Extension is for master 
 record gain.
MIXF_MONVOL Extension is for a monitor 
 source's gain.

MIXEXT_SCOPE_MASK Mask of possible scope 
 values.
MIXEXT_SCOPE_INPUT Extension is an input 
 control.
MIXEXT_SCOPE_OUTPUT Extension is an 
 output control.
MIXEXT_SCOPE_MONITOR Extension relates to 
 input monitoring.
MIXEXT_SCOPE_OTHER No scoping hint provided.

The argument is a pointer to an oss_mixer_enuminfo structure, which is defined as follows:

typedef struct oss_mixer_enuminfo {
 int dev;
 int ctrl;
 int nvalues;
 int version;
 short strindex[255];
 char strings[3000];
} oss_mixer_enuminfo;

The argument is a pointer to an oss_mixer_value structure, defined as follows:

typedef struct oss_mixer_value {
 int dev;
 int ctrl;
 int value;
 int flags; /* Reserved for future use. 
 Initialize to 0 */
 int timestamp; /* Must be set to 
 oss_mixext.timestamp */
 int filler[8]; /* Reserved for future use. 
 Initialize to 0 */
} oss_mixer_value;

The parameter changes requested in the ioctl are invalid or are not supported by the device.

The device or extension referenced does not exist.

Symbolic link to the pseudo mixer device for the system

Sound status device