[RFC 1/8] serial:st-asc: Add ST ASC driver.

[Russell King - ARM Linux]

On Wed, May 08, 2013 at 09:36:13AM -0700, Greg KH wrote:
> On Wed, May 08, 2013 at 06:31:48PM +0200, Arnd Bergmann wrote:
> > On Wednesday 08 May 2013, Greg KH wrote:
> > > > just mention there is not hardware reason to not use the generic ttySx
> > > > in place of ttyAS as we have only one IP that handle serial on this
> > > > family of SoC
> > > > 
> > > > personally I'll switch to ttySx
> > > 
> > > Great, then you can use the same major/minor range as well, so there's
> > > no more objection from me about this :)
> > 
> > Does that work these days when you have kernel with multiple built-in
> > uart drivers?
> 
> It "should", as the major/minor registration should only happen when the
> hardware is found, but I haven't tested it out, so I can't say for sure.

serial stuff has never operated like that.  More specifically, it's a
limitation with the tty stuff that the way stuff works is that a
tty driver can only drive a single bunch of contiguous minor numbers.
No interleaving is allowed.

That limitation has existed for years, and I don't see it going away.
As long as that limitation exists, you can only ever have one serial
driver driving a set of contiguous minor numbers.

There has been an attempt to "work around" this by making the 8250
driver "special" which was a complete hack to get it to work.  That
was while I maintained this stuff and I outright refused to make one
serial driver magically special.