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

[Alain M.]

Hi Harald,

IMHO, if you are planning such an upgrade to the ARM architecture, you 
should make it compatible with Cortex-M3 too. The differences are small 
but you could get to a dead-end if not planned.

FWIW I generaly agree with all the rest. The stack seems to be a big 
problem.

Alain

Harald Kipp escreveu:
> I'll try to summarize our status. Please read this carefully and let me
> know if something is missing or misunderstood.
> 
> 
> 1. Running in supervisor mode like now is plain wrong. At least the
> application code should use the user mode registers.
> 
> 2. Running applications in user mode is optimal, but the current code
> wouldn't work anymore because NutEnterExitCritical() changes CPSR.
> 
> 3. A final decision about how to switch to what mode when entering
> kernel routines need further discussion and probably a sample for
> testing. A preferable approach is to make this configurable, so the
> application developer may decide.
> 
> 4. Like item 3 regarding kernel routines, to some extend the same is
> valid for interrupt routines. Application developers may prefer to run
> interrupt routines in user mode for nesting interrupts.
> 
> 5. As a first action we can change all ARM related crt routines to
> properly set the user stack and enter NutInit in system mode. This is
> easily done and shouldn't harm existing code.
> 
> 
> Harald
> 
> 
> 
> 
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