Re: [PATCH] Stop pmac_zilog from abusing 8250's device numbers.

Russell King
2007-04-04T18:16:04Z

On Wed, Apr 04, 2007 at 01:41:53PM -0400, Theodore Tso wrote:
> On Wed, Apr 04, 2007 at 09:16:42AM -0700, H. Peter Anvin wrote:
> > One option would be to move the 8250-based serial ports, to, say,
> > /dev/ttyN* (for National Semiconductors -- the best I could come up
> > with) and redefine /dev/ttyS* as a serial port multiplexer which maps in
> > all the types, for the ones that really want dynamic mapping.
>
> > Of course, now you have the potential of aliasing, again, which tends to
> > cause all kinds of headaches w.r.t. locking.
>
> That would break the 99.9% of the the world using Intel-based systems
> which only have 8250's, for very little gain.
>
> Like it or not, /dev/ttySx and 8250 UART's are to serial ports what
> the PCI is to system buses....

And the simple answer to this (oh I've been here before) is to leave
the existing serial allocations well alone.

Then, you allocate a new major number and device name for the dynamically
assigned space and arrange for the serial layer to map these new chardevs
to the real serial ports.

*However* you still run into the issue that you do not know how many
serial ports you will need to register a tty driver with the tty layer.
Solve that technical problem and the idea of having a single namespace
for chosen serial ports and 8250 ports suddenly becomes realistic.

Continue ignoring that problem and this thread will just grow with zero
real progress.

I'm repeating myself though.

--
Russell King
Linux kernel 2.6 ARM Linux - http://www.arm.linux.org.uk/