On Mon, Jun 24, 2013 at 17:14 -0600, Stephen Warren wrote:
>
> [ active low pins, individually for sets or even single pins ]
>
> Can't you add this enhancement as follows:
>
> Update the driver to look at the per-pin GPIO flags in all cases.
> Presumably in any existing cases, those flags all say "active high"
> anyway, since specifying anything else was useless. In the very unlikely
> case this isn't true, one could always add a quirk based on the
> HW-specific compatible value.
Maybe I missed something, but
- is "the 'active low' property of a GPIO pin" something platform
specific? (maybe ARM inspired, introduced with pinctrl features)
- is it only available for specific GPIO controller drivers
("chips" or "banks"), or is it in some layer on top of gpiolib?
- is it in some other tree or branch than mainline?
Documentation/gpio.txt suggests and eyeballing the gpiolib.c
source supports (v3.10-rc7) that the in-kernel API doesn't have
an 'active-low' for pins. There is one for the sysfs API and
pins that were exported to user space, but not for in-kernel use.
This fits with my observation that application drivers on top of
gpiolib often take care of such a property which actually looks
like it would belong to the physical attachment.
I understand that a chip's driver will hide when a SoC's pin is
inverted, but I cannot see where gpiolib provides a means to hide
an externally connected inverting driver.
virtually yours
Gerhard Sittig
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