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

[Joe Hershberger]

Hi Marek.

On Mon, Nov 5, 2012 at 5:10 PM, Marek Vasut <marex at denx.de> wrote:
> 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.

It's not a problem of something being sent to the serial port.  It's
the call to serial_init() in arch/*/lib/board.c that kills it.  That
call needs to be no-op-able.

-Joe