Messages in this thread | | | Date | Mon, 1 Mar 2010 10:35:50 +0000 | From | Mark Brown <> | Subject | Re: [PATCH 1/3] gpiolib: add gpio_set_direction() |
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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. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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