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    SubjectRe: RFC: gpio: mmio: add support for 3 direction regs
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    On 01/03/2019 10:51 AM, Fried, Ramon wrote:
    >
    > On 1/3/2019 10:07, Vladimir Zapolskiy wrote:
    >> Hi Ramon,
    >>
    >> On 01/03/2019 09:36 AM, Fried, Ramon wrote:
    >>> Hi.
    >>>
    >>> I'm working on a driver for STA2X11 GPIO controller who seems to fit
    >>> best to the generic mmio driver,
    >> I hope you have seen the existing driver drivers/gpio/gpio-sta2x11.c
    > I surely did. we have the same IP in our soc but it was changed a lot
    > internally, don't want to litter the original.
    >>
    >>> the only problem I have is with the dir register case. The STA2X11
    >>> has 3 registers for dir, one for data, one for set and one for
    >>> clear. The generic-mmio driver has support for this fashion for the
    >>> dat & set & clear registers but not for dirout/dirin registers.
    >>>
    >>> I wonder if support for this is generic enough to deserve a patch, if
    >>> so I'm willing to quickly add this support, if not, adding a flag
    >>> such as below, will allow partly using the generic mmio driver only
    >>> for set/get and the direction can be handled outside the driver.
    >>>
    >> If gpio-mmio fits well, then it might be simpler to set a flag
    >> BGPIOF_UNREADABLE_REG_DIR, then call bgpio_init() and then overwrite
    >> .direction_input, .direction_output and .get_direction callbacks,
    >> as a reference you can take a look at gpio-74xx-mmio.c
    >
    > Nice.
    > That's an option I didn't think of, better than setting the flag.
    > what about adding the generic support ?

    Setting a GPIO direction over three different registers doesn't sound
    as a suitable candidate for generalization, also your particular
    implementation is partial, relies on external platform/driver code
    to preset the directions and it does not allow to change direction
    in runtime, so just renounce the idea.

    --
    Best wishes,
    Vladimir

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