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    SubjectRe: [PATCH v3 0/6] RTL8231 GPIO expander support
    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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