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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