Hi Kim,
o LCRR_PDYP, granted dangerous in your case, is obviously a writeable bit (not read-only), and documented as such in later documentation. In fact, there are no non-writeable bits in LCRR.
Well, "reserved" != "non-writable" (usually there is a comment that writing reserved bits produces undefined behaviour) so I agree with Heiko that as long the documentation that we have access to, designates bits as reserved, it makes sense to have such a mask.
o the user loses visibility into what is going on if they decide to drop/add sensitive bits such as LCRR_DBYP in their board's CONFIG_SYS_LCRR settings, and there's a mask lurking in the background.
o let's be practical here - in a board port, LCRR settings have to be paid attention to, no matter what hidden behaviours or new bits there are lying underneath - perhaps the form of 'protection' you seek is in the form of a comment in the code?
So what is it that you propose? That Heiko uses a LCRR in his board config (over-)writing reserved bits?
Cheers Detlev