GSoC DVB midway point

["Jeremy Morse" <jeremy.morse%gmail.com@localhost>]

This is an update for the GSoC DVB framework project - some more
information at the link below [1].

So far I've
 - Implemented a driver interface for DVB device drivers,
 - Implemented user ioctls and controls matching LinuxTV
 - written a test driver for the above, feeding a sample transport
stream to a user application (VLC) and displaying a picture.

The framework portions just about work, although I still need to
implement code to handle a couple of possible errors, and allow
drivers to de-register themselves. This roughly fits in with the
original timeline, from now I'll continue to improve the framework
part, but also create a driver for some actual dvb hardware, to
demonstrate this all works.

Like many other GSoC students, academic timings caused some trouble,
and cut two or three weeks out of the initial coding period through
exams and deadlines. Otherwise, getting to grips with a new code base
and build process took some time.

Probably the most difficult part of this for me is thinking through
possible race conditions and protecting against them, while also not
causing deadlocks - simple to do, but requires careful thinking. I've
not encountered any particular difficulties - aside from giving a
mutex too high an SPL then starting some IO while holding it, which
caused the machine to unexpectedly hang up. Otherwise I've been lucky,
with no particular project-stopping faults.

[1] http://netbsd-soc.sourceforge.net/projects/dvb/

Jeremy Morse