Open Bouteillebleu opened 11 years ago
Yeah, you can't access the fields of a register outside of a "with" block, because of the read-modify-write requirements. It shouldn't just crash, obviously :)
For read-only registers it may be okay to support directly reading, but there's still a potential problem for registers that are read-only to the CPU but not constant - allowing them to be read outside of a with block means you can inadvertently read an inconsistent snapshot of two fields that should be read atomically.
Reproduction steps:
You get the following error: Traceback (most recent call last): File "", line 1, in
File "/initrd/metal/bits.py", line 65, in get
File "/initrd/metal/bits.py", line 46, in extract
TypeError: unsupported operand type(s) for &: 'NoneType' and 'long'
From looking into this, this is because:
So if I'd set the values of a field first I'd expect this to be okay.
But in a read-only register like main_id, it doesn't make sense to do that - and yet nowhere in setting up the register does self._cachedvalue gets set, so any attempt at get on any of main_id's fields will cause a TypeError.