Re: [PATCH v4 02/10] pinctrl: mvebu: dove pinctrl driver

From: Linus Walleij
Date: Tue Jun 18 2013 - 11:23:09 EST

On Tue, Jun 18, 2013 at 5:11 PM, Russell King - ARM Linux
<linux@xxxxxxxxxxxxxxxx> wrote:
> 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?

Usually, like for syscon, you create an MFD hub which
carry the regmap.

> That sounds more heavy-weight than is really necessary.

May be so, especially if there is just one register to protect.
The usefulness of MM-regmap increase with the set of registers
needing to be protected.

Linus Walleij
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