Messages in this thread | | | Date | Tue, 01 Jun 2021 13:41:57 +0200 | From | Michael Walle <> | Subject | Re: [PATCH v3 0/6] RTL8231 GPIO expander support |
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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?
> So the regmap config is really important to get right. > > IIUC one of the ambitions around Rust is to encode this > in how memory is specified in the language. (I am still > thinking about whether that is really a good idea or not.)
-- -michael
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