LAI misunderstanding of the Preserve field property(?) about lai HOT 2 OPEN

This is caused by the following code unconditionally doing a read to get the original value.

One solution would be checking that the write only affects a part of the word, and only doing the read if that is the case.

I'm unsure whether the extra unused read is actually a problem? I suppose it could potentially confuse some hardware that do things on register reads, and it's probably better to stick to what ACPICA does if we want to work on real hardware.

from lai.

I'm unsure whether the extra unused read is actually a problem? I suppose it could potentially confuse some hardware that do things on register reads, and it's probably better to stick to what ACPICA does if we want to work on real hardware.

Yeah it's pretty much impossible to say, it might trip up some hardware, might not. There are probably some registers cleared by read? Another thing I thought of is if this was some other address space (aka not SystemMemory or SystemIO) but say SMBus. There a spurious read could cause more problems probably. At the very least it's extra wasted cycles or stalls for no reason.

from lai.