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    SubjectRe: [PATCH] OMAP3 GPIO: Fix getting the value of the GPIO output pin
    From
    2009/2/9 David Brownell <david-b@pacbell.net>:
    > On Sunday 08 February 2009, Joonyoung Shim wrote:
    >> > Which should clearly be AE6_34XX_GPIO141_OUT since it does
    >> > not enable the input driver. Try making that ...PIN_OUTPUT
    >> > read ...PIN_INPUT and see if things behave.
    >>
    >> Of course, it will be better if the name is clear as AE6_34XX_GPIO141_OUT.
    >> but, the core of this problem is not it, the chip->get() called in
    >> gpiolib_dbg_show()
    >> of drivers/gpio/gpiolib.c or dbg_gpio_show() of arch/arm/plat-omap/gpio.c
    >> can return the wrong value when gpio pin is configured as an output.
    >
    > No, the core of the problem is that you're using a GPIO
    > which is explicitly configured as output-only ... but are
    > treating it as if it were a normal bi-directional GPIO.
    >
    > It's acting *exactly* right for an output-only GPIO. But
    > that's not the behavior you expect, or want.
    >
    > If you weren't disabling the input driver, then when you
    > ask for the input value it would work as you expect. Which
    > is why I suggested you change how that ball is configured.
    > (That's actually a bugfix to those muxing tables ...)

    I understood that you say, ths PIN_OUTPUT flag must use
    when GPIO pin is output-only, and i got the result i want
    after GPIO pin is configured as bi-diretional GPIO.

    But i wonder why don't control in gpio_get() of arch/arm/plat-omap/gpio.c
    when the GPIO pin is output-only?

    thank you.

    - Joonyoung

    >
    > - Dave
    >
    > p.s. This specific confusion is new on OMAP3; previous
    > OMAPs didn't have the extra byte of options to
    > configure. The PIN_INPUT flag was, on previous
    > chips, effectively hard-wired on for GPIOs.
    >


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