On Thu, Oct 25, 2018 at 02:47:59PM +0100, Richard Fitzgerald wrote:

access. What does regmap debugfs do if you don't have a readables
list? Just reading a debugfs shouldn't be able to kill the hardware.
You might need to add a precious list which is more error prone
than listing the valid readables we are using.

It assumes everything is readable unless it's explicitly told otherwise
or the register map is overall write only (like a 7x9 one).  You could
mark the registers as precious to cause it to only do explicit I/O
operations on them but that's not what you mean and won't be as good a
guarantee that nothing can trigger a read.