[En-Nut-Discussion] arm port (RFC: Changing ARM mode)

[Ole Reinhardt]

Hi Harald,

> >> In which cases would we need 'enter kernel routine'? In some interrupt
> >> driven functions? All other driver code shold just run fine in user
> >> mode, does it?
> > 
> > At least NutEnter/ExitCritical() won't work in user mode, if I correctly
> > understood the ARM documents.

Ah ok, I see the problem.
 
> >> For me it sounds much cleaner to run as most code as possible in user
> >> mode and implement such context switch functions???
> > 
> > Do you have any idea, what else is disabled in user mode?
> > 
> > Protected OSes use an exception like SWI to switch the mode. No idea how
> > to implement this in Nut/OS, where the kernel is a bunch of libs only.
> 
> After some unpleasant experience with the interrupt handling discussion
> in this list a few months ago, please let me appeal to everyone, that
> several people are impatiently waiting for the next stable release.
> Please take any possible effort and time frame into your considerations.
> Specifically to Ole: I do have the stack backtrace running, but it will
> crash with the current mode the system is running in. So we need a
> decision before I can check it in. In the meantime I updated the
> documentation at
> http://www.ethernut.de/en/documents/arm-exceptions.html

Cool! And: No problem with the delay. I used the meantime with the
Ethernut5 Linux port. Just finished my first OE Image for Ethernut5
today and will test it tomorrow. Kernel and u-boot are up and running
and I just used a userland image from another board. So Linux on
Ethernut5 is just a few steps away...

> The interrupt problem was unpleasant, because a lot of very good ideas
> had been suggested here, but actually no working code had been
> presented. After some weeks people start asking what happened to the
> announced version 4.6 and I finally decided to fix the interrupt problem
> by using the quick and dirty solution I had in mind initially to speed
> things up. This probably frustrated some of the people, who spent their
> valuable time discussing more advanced solutions. Unfortunately this
> fruitful discussion died after my ignorant behavior towards the release
> of 4.6. I'd like to avoid this for 4.8.

Yes I know. We should restart this discussion. Perhaps after the 4.8
release. Than everybody could calm down a bit an perhaps we can sort
all these Ideas again.

Bye,

Ole


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