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Re: New CPM/DPRAM allocator
On Wed, 2003-03-19 at 04:07, Nick Garnett wrote:
> John Dallaway <jld at ecoscentric dot com> writes:
>
> > A few of questions:
> >
> > 1) Does this incompatibilty affect _all_ targets which run both RedBoot and
> > eCos?
>
> Just PowerPC QUICC targets, like the MBX, Adder or Viper, for example.
>
> > 2) Could the new allocator implementation be modified in any way to preserve
> > compatibility?
>
> Possibly. But I'll defer to Gary on this one.
>
The more I look at this, the less I understand why it fails now. The
new allocation scheme should not clash - i.e. mixing new eCos with old
RedBoot should be OK.
Perhaps if I can figure out why this is failing, I can propose a change
which will not cause problems.
> > 3) To what extent might the new allocator perturb eCos functionality other
> > than by a stepwise "it will work or it will be completely broken".
>
> It shouldn't affect anything else. Failure modes are hard to specify
> since they depend on the contents of what is currently an
> uninitialized location in RAM. Different instances of RedBoot might
> have different values there.
>
> We might even be able to add a test to the DPRAM code to detect an old
> RedBoot and generate an error message before proceeding.
>
> > 4) Is a further break in compatibility possible as potential issues with the
> > new allocator are ironed out?
>
> Unlikely. The code is only a handful of lines.
>
> >
> > We need to determine how to manage the switch over to the new CPM/DPRAM
> > allocator smoothly for everyone. From my perspective, it is certainly
> > unfortunate that this innovation has arrived between 2.0 beta and 2.0
> > final. Were it not for the break in compatibility, I would vote against
> > incorporating this change for 2.0 final since the change will (to a certain
> > extent) invalidate beta testing by the net community. However, it would
> > also be undesirable for 2.0 final RedBoot to be incompatible with anonCVS
> > eCos from day 1. Users are likely to want to stick with a release version
> > of the firmware while experimenting with eCos from anonCVS.
> >
>
> It only affects a handful of boards: MBX, VIPER, ADDER, TS1000. QUICC2
> targets like the tS6 and VADS are not affected, and non-QUICC MPC8xx
> targets like the CMA28x and FADS boards are not affected.
>
> --
> Nick Garnett eCos Kernel Architect
> http://www.ecoscentric.com/ The eCos and RedBoot experts
--
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