[Question] Can I open a substream in kernel space without attach to a file pointer?

["Bryan Wu" <cooloney@kernel.org>]

Hi Takashi,

I am developing a USB gadget driver compliant to USB Audio Class Spec 2.0.
So I want to open a PCM substream and do some playback of capture,
then close them?

I found snd_pcm_open_substream() is for opening a substream and attach
it to a file.
But in my application, there is no need to open a file before opening
a substream.

- Is there any interface for me to open a substream in kernel space
without attach to a file?
- How to playback and capture in kernel space, use snd_pcm_lib_write
and snd_pcm_lib_read?
- How to get the snd_pcm_hardware struct from low level driver,
because I have to get the hardware configuration of the snd pcm
device?

And I am reading the code of OSS emulator in ALSA. It provides some
info about the kernel space sound card programming.

Thanks a lot
-Bryan