Re: [PATCH v1 04/12] input: matrix-keypad: push/pull, separate polarity

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



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
-- 
DENX Software Engineering GmbH,     MD: Wolfgang Denk & Detlev Zundel
HRB 165235 Munich, Office: Kirchenstr. 5, D-82194 Groebenzell, Germany
Phone: +49-8142-66989-0 Fax: +49-8142-66989-80  Email: office@xxxxxxx
--
To unsubscribe from this list: send the line "unsubscribe linux-input" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html




[Index of Archives]     [Linux Media Devel]     [Linux USB Devel]     [Video for Linux]     [Linux Audio Users]     [Yosemite News]     [Linux Kernel]     [Linux SCSI]     [Linux Wireless Networking]     [Linux Omap]

  Powered by Linux