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SubjectRe: Universal Driver Interface spec available
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> Intel has also made statements to the effect of reference drivers for it's
> hardware are most likely going to be UDI. If this happens, you are going to
> want UDI support just so you can bring up new Intel hardware fast.

Slowly you mean. I've read the UDI spec in detail. Its about fit for BIOS
loaders but thats it. If intel provide source it will be worth porting their
drivers to the OS properly. If intel don't provide source we don't care anyway.

You simply cannot express stuff like the linux parport sharing in UDI, its
got no equivalence. Out goes parallel devices. You can't portably express
the Linux tty layer, out go tty devices. It's too slow for serious networking
and it can't properly express our scsi stuff and make good use of it.

So what are you going to do with it. Joysticks ?

> With some work on the UDI interface, you should be able to make it so all
> UDI drivers are RTLinux friendly. Also, you could change the
> mutex/semaphore/locking code as many times as your little hearts desire
> without having to rewrite every UDI driver. The UDI interface has all of the
> mutex and timed waits happening outside the driver, in the UDI support
> routines.

Which can have very long lock holding times. Not funny at all.

> I would have thought that people would rather spend their time working on
> improving the operating system rather than rewrite an ethernet or SCSI
> device driver for the umpteenth time. That is what UDI is intended to allow
> you to do, focus on the OS and use standard drivers.

UDI can't correctly express the Linux resource management in a portable way,
nor the memory allocator, nor the layering stuff.

> How about just a documented driver interface that doesn't change? The
> interface has changed for EVERY KERNEL VERSION lately.

If you dont change you get the windows 98 problem.

> The 2.0 drivers had to be modified for 2.2. I believe I've seen indications
> that further SMP patches will make it necessary to change the drivers again
> for 2.4, although I haven't found any documentation that clearly spells this
> out.

Yes some will. But as with 2.0 the changes so far to do a simple job are
easy.

> Where is the documentation on writing drivers for Linux? I've got the Rubini
> book, which is stuck back in kernel version 1.2 for a lot of stuff. There
> are enough changes where none of his examples compile correctly under 2.2.
> It wasn't until I started compiling stuff that I found out that the PCI
> interface had changed, I have no idea how many other things have changed
> since the time of the book.

Rubini's book is apparently being updated. I have written a set of articles
for Linux Magazine on 2.0->2.2 conversions - you can grab them from
O'Reilly's web site or buy the magazine 8)

There is a project going on to write a complete, thorough Linux kernel
book on the net. There are 2 or 3 other kernel books too.

Alan


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