Re: Serial consoles (was: [Ksummit-2013-discuss] [HOBBYIST ATTEND]IIO maintainer and developer)

From: Pavel Machek
Date: Thu Oct 10 2013 - 02:50:50 EST



On Thu 2013-09-19 09:15:13, Geert Uytterhoeven wrote:
> > On Thu, Sep 12, 2013 at 10:12 PM, Rob Landley <rob at landley.net> wrote:
> > > 3) QEMU command line to boot to a shell prompt with serial console. x86 is
> > > ttyS0, arm versatile is ttyAMA0, sh4 is ttySC1. Get it wrong and you have no
> > > output.
> >
> > Can't we long-term fix this? Can we bring up both say ttyS0 and ttyAMA0
> > on a machine and remove the other one when the first is opened,
> > then print a friendly reminder to move over to ttyS0 if ttyAMA0 is
> > used instead, so people are encouraged to switch to ttyS0
> > for everything over time?
> >
> > Or do these separate serialport namespaces have a real utility?
>
> I'd say they make life more difficult.
> Making it easier to distinguish ports may have been the original reason, but
> in other subsystems ("SCSI" disks, Ethernet ports, IDE, ...) there is a uniform
> device namespace.
> We still have different namepaces for other types of block devices, though, but
> that's (usually) handled automatically by udev, file system UUIDs, etc.
>
> Note that on m68k we never followed the non-16550-ports-should-use-a-different-
> name-franze, and always continued using /dev/ttyS* for all serial ports.

Well.. spitz (ARM) does the same -- registers ttyS0 for its serial ports. But then
I plugged bluetooth CF card... with 16550 port... and things got "interesting".

I don't think it was ever solved, as serial layer does not support uniform device
namespace...

--
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