[PATCH v4 2/3] powerpc/xmon: drop the nobt option from xmon plus minor fixes

[Michael Ellerman]

"Guilherme G. Piccoli" <gpiccoli at linux.vnet.ibm.com> writes:

> On 03/30/2017 09:36 PM, Paul Mackerras wrote:
>> On Wed, Mar 22, 2017 at 04:27:50PM -0300, Guilherme G. Piccoli wrote:
>>> The xmon parameter nobt was added long time ago, by commit 26c8af5f01df
>>> ("[POWERPC] print backtrace when entering xmon"). The problem that time
>>> was that during a crash in a machine with USB keyboard, xmon wouldn't
>>> respond to commands from the keyboard, so printing the backtrace wouldn't
>>> be possible.
>>>
>>> Idea then was to show automatically the backtrace on xmon crash for the
>>> first time it's invoked (if it recovers, next time xmon won't show
>>> backtrace automatically). The nobt parameter was added _only_ to prevent
>>> this automatic trace show. Seems long time ago USB keyboards didn't work
>>> that well!
>> 
>> Xmon still can't use a USB keyboard.  It's not a question of how well
>> USB keyboards work, it's that having a non-interrupt-driven USB stack
>> with (at least) an OHCI host controller driver and a keyboard driver
>> in xmon is impractical.
>
> That's nice to know Paul, thank you. Fortunately, we kept the automatic
> trace showing feature!
>
> Seems my commit message was unfortunate/wrong in this aspect, though.
> @mpe, if you wanna change, feel free. Although it's not essential...

It's already merged, so it is what it is.

I do remember not quite understanding what you meant with the "long time
ago" bit, but didn't think much more of it.

cheers