snd_pcm_get_apx_data()

Retrieve data from the acoustic library in an APX module

Synopsis:

#include <sys/asoundlib.h>

int snd_pcm_set_apx_data( snd_pcm_t *pcm,
                          uint32_t apx_id,
                          snd_pcm_apx_param_t *param,
                          void *data );

Arguments:

pcm
The handle for the PCM device, which you must have opened by calling snd_pcm_open_name(), snd_pcm_open(), or snd_pcm_open_preferred().
apx_id
The ID of the APX module you want to access.
param
The library parameter information and the size of the data to set.
data
A pointer to the location to store the retrieved data. If data is NULL, the size member of param is still updated with the minimum size required for the data buffer.

Library:

libasound.so

Use the -l asound option with qcc to link against this library.

Description:

Note:
This function can only be used if you have QNX Acoustic Management Platform 3.0 installed.

The snd_pcm_get_apx_data() function retrieves data from the acoustic library in an APX, as specified in the snd_pcm_apx_param_t structure that param points to:

typedef struct snd_pcm_apx_param {
    uint32_t    size;
    uint32_t    dataId;
    int32_t     channel;
    int32_t     status;
} snd_pcm_apx_param_t;

This structure includes the following members:

size
The size of the buffer that the data argument points to for snd_pcm_set_apx_data() and snd_pcm_get_apx_data(). For snd_pcm_get_apx_data(), the data argument can be NULL. On return, the size member is updated with the actual size of the retrieved data.
dataId
The identifier for the parameter whose value you want to access.
channel
The channel identifier. Used only for selected channel-based parameters. The channel number is zero-based and should be from 0 to one less than the maximum number of channels valid for the specified parameter.
status
The return code from the library; one of the QWA_* codes defined in qwa_err.h.

Because this function is only used with acoustic (SFO, SPM) APX modules, it must be called on the playback PCM device.

Returns:

0 on success, or a negative errno value if an error occurred.

Note:
You should check both the return value of snd_pcm_get_apx_data() and the status member of snd_pcm_apx_param_t to determine if a call is successful.

This function can also return the return values of devctl() (see devctl() in the QNX Neutrino C Library Reference).

Errors:

EINVAL
The handle pcm is not opened, the value of param is NULL, or apx_id is invalid.
ENOMEM
Not enough memory was available to copy the buffer.
ENODEV
The APX module specified by apx_id is not configured.

Classification:

QNX Neutrino

Safety:
Cancellation point Yes
Interrupt handler No
Signal handler Yes
Thread Yes

Caveats:

This function is not thread safe if the handle (snd_pcm_t) is used across multiple threads.

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