an array of fixed-sized channel_softc elements. This way IDE controllers
which more than 1 channel (pciide) can extend the channel data easily
for private needs.
To avoid the double dereference at runtime, change the argument of
wdcstart() to the channel data pointer instead of the array index.
that sc_ad.ioh is the 8-byte region as opposed to blindly passing it
the first region.
With this change, and a device def which will follow, the IDE controller
on my OPTi Audio 16 card works!
mycroft