[avrdude-dev] [bug #21954] verify fails for masked ('x') bits

[Matthijs Kooijman]

Follow-up Comment #2, bug #21954 (project avrdude):

Any comment on this issue? I'd like to get this fixed. I'm happy to help out a
bit if we can figure out how to fix it.

As for how things should work, I'd propose this:
 - For every single-byte memory (fuses, lock bytes), avrdude should know what
bits are used and which aren't.
 - When writing these bytes, any unused bits in the input are ignored and
fixed to 1 when the byte is sent to the programmer.
 - If any of the unused bits are specified as 0 in the input, avrdude should
show a warning recommending to set them to 1.
 - When reading these bytes, they should probably be displayed as returned by
the hardware.
 - When verifying these bytes, only the used bits should be compared, the
unused bits ignored.


The tricky part of implementing this, is how to tell avrdude what bits are and
aren't used. In theory, the information is already present as part of the
commands in avrdude.conf, but as #22248 suggests they aren't perfectly
consistent yet (right?).

If the commands can be made consistent it should be possible to scan the
commands to find out what bits are and aren't used (though I'm not 100% sure
if this applies to the more exotic hardware as well?).

Alternatively, the commands could be changed to always read and write full
bytes, and we could add an explicit mask byte in the config, which might be a
bit more straightforward?

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