Hi,
I am writing Alsa driver on 2.6 kernel for arm platform.
I want to test my driver with application.
I took one sample application & tried to map the functions.
******************* sample application *********************************
This program opens an audio interface for playback, configures it for
stereo, 16 bit, 44.1kHz, interleaved conventional read/write access. Then
its delivers a chunk of random data to it, and exits. It represents about
the simplest possible use of the ALSA Audio API, and isn't meant to be a
real program.
#include <stdio.h>
#include <stdlib.h>
#include <alsa/asoundlib.h>
main (int argc, char *argv[])
{
int i;
int err;
short buf[128];
snd_pcm_t *playback_handle;
snd_pcm_hw_params_t *hw_params;
if ((err = snd_pcm_open (&playback_handle, argv[1],
SND_PCM_STREAM_PLAYBACK, 0)) < 0) {
fprintf (stderr, "cannot open audio device %s (%s)\n",
argv[1],
snd_strerror (err));
exit (1);
}
if ((err = snd_pcm_hw_params_malloc (&hw_params)) < 0) {
fprintf (stderr, "cannot allocate hardware parameter structure
(%s)\n",
snd_strerror (err));
exit (1);
}
if ((err = snd_pcm_hw_params_any (playback_handle, hw_params)) < 0) {
fprintf (stderr, "cannot initialize hardware parameter
structure (%s)\n",
snd_strerror (err));
exit (1);
}
if ((err = snd_pcm_hw_params_set_access (playback_handle, hw_params,
SND_PCM_ACCESS_RW_INTERLEAVED)) < 0) {
fprintf (stderr, "cannot set access type (%s)\n",
snd_strerror (err));
exit (1);
}
if ((err = snd_pcm_hw_params_set_format (playback_handle, hw_params,
SND_PCM_FORMAT_S16_LE)) < 0) {
fprintf (stderr, "cannot set sample format (%s)\n",
snd_strerror (err));
exit (1);
}
if ((err = snd_pcm_hw_params_set_rate_near (playback_handle, hw_params,
44100, 0)) < 0) {
fprintf (stderr, "cannot set sample rate (%s)\n",
snd_strerror (err));
exit (1);
}
if ((err = snd_pcm_hw_params_set_channels (playback_handle, hw_params,
2))
< 0) {
fprintf (stderr, "cannot set channel count (%s)\n",
snd_strerror (err));
exit (1);
}
if ((err = snd_pcm_hw_params (playback_handle, hw_params)) < 0) {
fprintf (stderr, "cannot set parameters (%s)\n",
snd_strerror (err));
exit (1);
}
snd_pcm_hw_params_free (hw_params);
if ((err = snd_pcm_prepare (playback_handle)) < 0) {
fprintf (stderr, "cannot prepare audio interface for use
(%s)\n",
snd_strerror (err));
exit (1);
}
for (i = 0; i < 10; ++i) {
if ((err = snd_pcm_writei (playback_handle, buf, 128)) != 128)
{
fprintf (stderr, "write to audio interface failed
(%s)\n",
snd_strerror (err));
exit (1);
}
}
snd_pcm_close (playback_handle);
exit (0);
}
**************************************END***********************************
**************************************
I tried to trace back the application how i can map my driver routines with
the calls in application.
While tracing I couln't find the definition of of few functions like
snd_pcm_sw_params_set_start_threshold()
snd_pcm_hw_params_set_rate_near()
snd_pcm_hw_params()
snd_pcm_hw_params_free()
For few I could only find the prototypes.
My doubts are,
where can I find the definitions for these functions or Alsa APIs ?
Do i need to have any lib (alsa_lib) ?
If not how my driver can be accessed from application layer, I mean how
calls are mapped ?
Can anybody please help me in this regard.
Thanks
Pavana S
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