Messages in this thread | | | From | Linus Walleij <> | Date | Tue, 1 Jun 2021 13:48:43 +0200 | Subject | Re: [PATCH v3 0/6] RTL8231 GPIO expander support |
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On Tue, Jun 1, 2021 at 1:41 PM Michael Walle <michael@walle.cc> wrote: > Am 2021-06-01 12:51, schrieb Linus Walleij: > > On Tue, Jun 1, 2021 at 12:18 PM Michael Walle <michael@walle.cc> wrote: > >> Am 2021-06-01 11:59, schrieb Linus Walleij: > > > >> > Just regarding all registers/memory cells in a register page > >> > as default volatile (which is what we do a lot of the time) > >> > has its upsides: bugs like this doesn't happen. > >> > >> I don't think this is the bug here. If it is really a write-only > >> register > >> the problem is the read in RMW. Because reading the register will > >> return > >> the input value instead of the (previously written) output value. > > > > True that. Write and read semantics differ on the register. > > > > Volatile is used for this and some other things, > > like for example interrupts being cleared when a register > > is read so it is strictly read-once. > > Isn't that what precious is for?
I never figured that one out. But I assume you are right.
Proper regmap semantics documentation is forthcoming! ;)
Yours, Linus Walleij
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