[PATCHv2 3/7] pinctrl: gpio: vt8500: Add pincontrol driver for arch-vt8500

[swarren@wwwdotorg.org (Stephen Warren)]

On 03/27/2013 03:23 AM, Tony Prisk wrote:
> On Tue, 2013-03-26 at 14:28 -0600, Stephen Warren wrote:
>> On 03/25/2013 12:51 PM, Tony Prisk wrote:
...
>>> - #gpio-cells : should be <3>.
>>> 	1) bank
>>> 	2) pin number
>>> 	3) flags - should be 0
>>>
>>> I will clarify this in the next version.
>>
>> I think you should define a flag for inverted or active-low. This is
>> typically bit 0 in the flags cell.
>> ...
> 
> Stephen,
> 
> Do you know if there is an example of this somewhere I can look at?
> 
> I did a quick search through the documentation for pinctrl and gpio, but
> I can't find any code for defining active-low in the gpio flags. There
> seems to be plenty for defining interrupt 'modes' but nothing for
> setting active-low.

Interrupt modes would be for the IRQ binding, not the GPIO binding.

For an example, see:

Documentation/devicetree/bindings/gpio/

> grep -i polarity *
> gpio-74x164.txt:  the second cell is used to specify the gpio polarity:
> gpio-adnp.txt:  - bit 0: polarity (0: normal, 1: inverted)
> gpio_lpc32xx.txt:      - bit 0 specifies polarity (0 for normal, 1 for inverted)
> gpio-mxs.txt:  the second cell is used to specify the gpio polarity:
> nvidia,tegra20-gpio.txt:  - bit 0 specifies polarity (0 for normal, 1 for inverted)
> pl061-gpio.txt:  - bit 0 specifies polarity (0 for normal, 1 for inverted)

> I also couldn't see anywhere where it was possible to interpret the
> flags that are passed in. Assuming I add an .of_xlate, and pass, for
> example, *flags = gpiospec[2] I can't see anywhere later on where I get
> the chance to 'decode' the flags to perform the specific configurations.

of_get_named_gpio_flags() will return the flags.

For an example usage, see:

> drivers/mmc/core/host.c:369:		gpio = of_get_named_gpio_flags(np, "cd-gpios", 0, &flags);

(it's at that line in next-20130325 at least)