Re: [PATCH v3 3/7] gpio: regmap: Add gpio_regmap_operation and write-enable support

["Michael Walle" <mwalle@kernel.org>]

On Thu Jul 16, 2026 at 11:40 AM CEST, Andy Shevchenko wrote:
> On Thu, Jul 16, 2026 at 11:08:55AM +0200, Michael Walle wrote:
>> On Thu Jul 16, 2026 at 10:27 AM CEST, Andy Shevchenko wrote:
>> > On Thu, Jul 16, 2026 at 02:26:14PM +0800, Yu-Chun Lin wrote:
>
> ...
>
>> > From the above list I tend to the approach 2, but this might require to have
>> > GPIO regmap level of locking. I'm a bit lost in the context, though. I assume
>> > we need a fresh start, id est issue a v6 with approach 2 or 3 in place and
>> > summarize the choices in the cover letter, so we can understand what has been
>> > considered.
>> 
>> I don't really like approach 3. You'd need to check if the regs of
>> both xlate calls are the same. With the sample code above, you
>> silently drop the first xlate'd reg.
>
> If I rank the proposals, the worst is #1, the best is #2.
>
>> And honestly, it really seems like a one-off. What controllers, are
>> there that need a write enable bit. The real problem seems to be
>> the assumption that we operate on just one bit. IOW we either set
>> mask or don't set mask in gpio_regmap_set().
>
> Yes, we should KISS.

But IMHO #2 and #3 are not KISS. Approach 2 is just a way of adding
some kind of pre op to a gpio set. Just tying it to a write enable
feature. That kinda bothers me. It might also be useful for other
things, too. So don't tie it to just write enable. And who is doing
a write disable if it's not self clearing for example. Probably Some
kind of post op :)

Approach 3 is a way to change the value of the written value - in
a restricted way, as is is just doing a OR with both values.

Also approach 2 might not even work if the hardware requires the
write enable bit set in the *same* write as the gpio set bit. Thus,
we might need both anyway in the future.

>> For a more generic solution, we should be able to control the
>> written value. We could add another .value_xlate().
>
> Maybe not now?

But if not now, then when? I wouldn't add the write enable feature
and later a more generic solution which also covers the write enable
feature.

> As per IPs, Synopsys IPs (not exactly GPIO) likes to
> have that kind of "protection". So, from HW perspective it's kinda
> pattern, and it might be possible to see more IPs (including GPIO)
> that follow it in some cases.

-michael