<Chips4Makersaka4>
<jfng[m]1> "how can you write a read-any/..." <- One could allow caching the reserved bits e.g. read them once and use it as mask. The non-reserved bits will then be set by or them to the mask.
<Chips4Makersaka4>
But further thought is this does not need separate type but is a matter of documentation on how to use the reserved bits.
<Chips4Makersaka4>
* by or'ing them
<jfng[m]1>
it would also assume that the read value is constant, otherwise caching it would violate write-last
<jfng[m]1>
but anyway, i agree this is implementation dependent