From: Nicolas Boullis <nboullis@debian.org>
While working on an ALSA driver for the audio part of em8300-based MPEG
decoder boards (Sigma Designs' Hollywood+ boards and Creative Labs' DXR3
boards), I think I discovered a bug in the code that generates IEC958
subframes from linear samples (iec958 plugin): M and W preambles are
swapped, and B preambles should only be used on even subframes. The
attached patch fixes this issue.
- added link/unlink/link_fd fast_ops callbacks
- moved code from snd_pcm_link to pcm_hw.c
- moved "empty" routines pointing to slave to pcm_generic.c
- introduced snd_pcm_generic_t
The preamble values can be defined in iec958 plugin configuration.
As default, Z/Y/X=8/4/2 is used. CMI8338 has different values,
so override in its configuration.