On Tue, Jun 18, 2013 at 05:02:49PM +0200, Linus Walleij wrote:

Nowadays I would do the above with regmap_update_bits().

Mutual exclusion for read-modify-write of individual bits in a
register is one of those cases where doing a regmap over
a memory-mapped register range makes a lot of sense.
(drivers/mfd/syscon.c being a nice example)

So, for that solution we need to have some kind of global regmap per
register or somesuch.  Then you run into regmap needing a struct
device - well, with a shared register, which struct device do you
use, or do you have to invent one?

That sounds more heavy-weight than is really necessary.