snd_pcm_plugin_read()??

Hi all!
I’m audio app engineer.
I want to code pcm capture program.
Now io-audio is working.
But when snd_pcm_plugin_read function is excuted, scount member in
snd_pcm_channel_status structure is always zero, and status member in
snd_pcm_channel_status structure is zero(SND_PCM_STATUS_NOTREADY) too, in
spite of successing of snd_pcm_channel_params().
And when I read the snd_pcm_info structure,
flag member is 0x101(PLAYBACK || SHARED), not CAPTURE.

How can I slove this problem, and what do I mistake and miss for that
problem.
Please Help me, wait for replying of wise men.