Hi.  I've done a lot of RTOS (VxWorks and VRTX) and NON-RTOS work creating
device drivers; i.e., working at the hardware interfacing level.  I've also
done some real-time UNIX work and some Linux Embedded application
development, but I've never worked at the device driver level w/ either of
these OS's.  In general, I have been told that it is much more difficult to
interface to devices via Linux and it takes much longer.  Where I use to
work, the guys have a lot of war stories of how long it took to do the
development at this level and I am about to step into it myself.

Is there a general rule, say it takes me a week to write the software to a
SEEPROM in an RTOS would it take twice as long (or longer) with Linux?  For
example, I have a friend that was given a sample device driver to a device
very similiar to a SEEPROM and it took him a little over 3 weeks to complete
(and this is after inheriting it from the guy that was working on it).  To
me using VxWorks, I believe I could have pumped this out in a week.

Secondly, I need to be able to sit on an interrupt from a UART FIFO and
stuff characters into to it everytime the flag says half-empty (hi-speed
stuff).  I do not want to 'poll' this, I want to write an ISR to handle
this.  Is this difficult to do in Linux and is there any place that I can
find an example of this type of work?

Thanks.