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    SubjectRe: [PATCH 1/3] gpiolib: add gpio_set_direction()
    On Sat, Feb 27, 2010 at 09:51:08AM -0800, David Brownell wrote:
    > On Saturday 27 February 2010, Mark Brown wrote:

    > > Indeed, but some devices do implement a distinct tristate state for  
    > > input mode pins (disabling interrupt generation logic and so on for  
    > > example).

    > That's a pretty sloppy usage of the term "tristate" ... yeah, there
    > are people who take glee in abusing terminology to introduce confusion,
    > and some of them write technical manuals with little regard to normal
    > usage of terms (or trademarks, which do exist for "tristate").

    It's a bit clearer when the pins have multiple functions of which GPIO
    is only one - normally the tristate is something that applies over all
    the functions of the GPIO.

    > IRQ generation logic should be disabled until request_irq() code paths
    > report otherwise. And regardless, whether a GPIO triggers an IRQ has
    > nothing at all to do with its "direction".

    This is an internal Linux implementation issue rather than a hardware
    one - that was just an example one of the things that tristating the pin
    rather than just putting it into input mode does.
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      Last update: 2010-03-01 11:39    [W:0.026 / U:4.168 seconds]
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