[U-Boot] [PATCH 2/2] serial: Make nulldev a serial device

[Marek Vasut]

Dear Joe Hershberger,

> Hi Marek,
> 
> On Fri, Nov 2, 2012 at 8:37 PM, Marek Vasut <marex at denx.de> wrote:
> > Dear Joe Hershberger,
> > 
> >> This allows the default console to be specified as the nulldev.  This is
> >> specifically helpful when the real serial console's init() cannot run
> >> early in the boot process.  When the init can be run, then the console
> >> can be switched to the real device using the std* env vars.
> >> 
> >> Signed-off-by: Joe Hershberger <joe.hershberger at ni.com>
> > 
> > Isn't it actually better to have null stdio device? Some systems might
> > not even use serial port (and so null serial will be useless on these
> > systems)!
> 
> As I described in my commit log, this is for the case where the serial
> and console init must not touch the hardware, (since it doesn't exist
> yet if it's in an FPGA or on a PCI or USB connection).  Making the
> default serial port be the nulldev avoids this issue.

So add nulldev serial device for this stupid case. Even though fixing iomux such 
that it'd not send anything to serial port at all if nulldev is selected would 
be even better idea.

That won't work?

> As for systems with no real serial port, there can still be the
> nulldev serial device... or not.  Why is that a problem?
> 
> -Joe

Best regards,
Marek Vasut