[avrdude-dev] [bug #30680] Checking for all 0xff not best way to decide which pages to program

[Joerg Wunsch]

Update of bug #30680 (project avrdude):

                  Status:                    None => Duplicate              
             Open/Closed:                    Open => Closed                 

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Follow-up Comment #1:

I know that the current implementation leaves a bit to be
desired.  Alas, there's currently nobody who has the time
and energy to implement the complete rework that would be
needed in order to avoid the underlying problem, that any
actual file information is lost by the time the programming
is started.

Anyway, you (respectively your bootloader) makes one
assumption which is fundamentally wrong, and which in turn
gives the implementation the right to skip any flash cell
that would be written to 0xffff: flash bits can _only_ be
written from 1 to 0, consequently, any attempt to write a
1 bit is essentially a nop.  As it is a nop, it can be skipped.
(In order to return a flash cell back to 1 bits, it must be
erased.)

The problem here is apparently an implementation flaw in the
Arduino bootloader.  It has already been discussed in
bug #30061, so I'm closing this bug here as a duplicate of
that one.

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