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ISR Argument Proposal Request



Joel Sherrill writes:
 > 
 > 
 > gregory.menke at gsfc.nasa.gov wrote:
 > > 
 > > Joel Sherrill writes:
 > >  >
 > >  >   NOTE: When you change a port, I would consider that to include
 > >  >   getting all the BSPs modified.  Everything should still build.
 > >  >   I regularly build all BSPs so this is somethign I can provide
 > >  >   feedback on.
 > >  >
 > >  > We can't start this until we are confident all
 > >  > the ports will get updated.
 > > 
 > > I can work on the mips side and test it on our hardware once theres
 > > consensus on the implementation.
 > > 
 > > I would like to preserve the ability to pass a pointer to the stack
 > > frame to the vector, preferably as an extra argument to the vector
 > > call itself.  This is essential for some of our interrupt processing
 > > and avoids unpleasant hacks.  In fact, we don't use the vector # at
 > > all at present.
 > 
 > I hesitated mentioning this but in fact a handful of 
 > ports which pass a 2nd argument which is the address of the
 > exception/interrupt stack frame.  The format of the data
 > at that pointer is port defined although I believe the
 > name of the data type is universal.  So I would REALLY
 > like to see:
 > 
 > void _ISR_HANDLER( void *, frame * );
 > 
 > with better names.  :)
 > 
 > The frame * is generally also known at ISR vectoring time.
 > 

At present cpu.h provides a per-cpu #define for conditionally
including the 2nd stack frame parameter- its not accessible by
configure.  Perhaps that approach could stay if people desire it- a
2nd parameter is inexpensive on mips, but not necessarily elsewhere.

I've come into this discussion a bit late, my interpretation of the
discussion is people are contemplating changing the vector table to an
array of structs, one per vector, which contain the vector address and
a user-supplied void * which is passed with the vector call.  Each bsp
will index into the array as it suits the architecture- the advantage
of the structs being it allows the programmer to supply something
useful rather than having to interpret a vector # or creating a pile
of small functions to do it.  Is this right?

On the mips, we vector exceptions from the same table as interrupts,
which I think is a wash in this case as we would set the void * to the
exception #.

Gregm