On line 63 of [this example header file](http://alsa-project.org/alsa-doc/alsa-lib/control_8h-source.html) there is a typedef:

```
typedef struct _snd_ctl_elem_info snd_ctl_elem_info_t;

```

There are multiple examples of typedefs like that through the code.
My goal is to get to the actual definition of the structure `_snd_ctl_elem_info` but I have grepped the source and googled but found no traces of the actual definition. Because of this search failure, I've started to think I might be missing some concepts and it might be something to do with kernel and backwards compatibility?

My motivation for this is to be able to gdb step through alsa and have an overview of the structures.

Is this some form of a low level structure definition pattern?