Re: [PATCH v3] iio: dac: Add support for the AD5592R/AD5593R ADCs/DACs

[Michael Hennerich <michael.hennerich@analog.com>]

On 03/11/2016 05:37 PM, Linus Walleij wrote:
> On Mon, Mar 7, 2016 at 7:34 PM, Michael Hennerich
> <michael.hennerich@analog.com> wrote:
>> On 03/05/2016 03:32 PM, Jonathan Cameron wrote:
>
>>>> Changes since v2:
>>>>          * Use child nodes to describe channels
>>>>          * Fix probe return and driver remove path
>>>>          * Move locking closer to where its used
>>>>          * Remove WARN_ON but return error
>>>>          * Remove OPEN DRAIN configuration option
>>>
>>> Why? I don't particularly mind as of course you aren't obliged to support
>>> every option in a driver, but I'm curious ;)
>>
>> I'm not aware that someone asked for that feature.
>> Supporting it the proper way requires a new GPIOF flag for gpiolib, which we
>> can still discuss later, in case someone asks for it.
>
> We have:
> include/dt-bindings/gpio/gpio.h
>
> /*
>   * Open Drain/Collector is the combination of single-ended active low,
>   * Open Source/Emitter is the combination of single-ended active high.
>   */
> #define GPIO_OPEN_DRAIN (GPIO_SINGLE_ENDED | GPIO_ACTIVE_LOW)
> #define GPIO_OPEN_SOURCE (GPIO_SINGLE_ENDED | GPIO_ACTIVE_HIGH)
>
> So consumers can ask (in DT) for a line in open drain mode.
>
> FLAG_OPEN_DRAIN will be set internally in gpiolibs gpio_desc
> in of_find_gpio() as a result and it will behave as expected.
>
> Yours,
> Linus Walleij
>

Hi Linus,

The thing is that the device directly supports an OPEN DRAIN mode.

If the consumer asks for open drain mode - everything works as expected.
However instead of utilizing the on-chip feature, GPIOLIB will emulate 
open drain behaviour by configuring the chip for input when someone 
writes logic high.

So the comment above was really meant to say -
remove on-chip OPEN DRAIN mode, consumers should use the GPIOLIB 
implementation if required.



-- 
Greetings,
Michael

--
Analog Devices GmbH      Wilhelm-Wagenfeld-Str. 6      80807 Muenchen
Sitz der Gesellschaft: Muenchen; Registergericht: Muenchen HRB 40368;
Geschaeftsfuehrer:Dr.Carsten Suckrow, Thomas Wessel, William A. Martin,
Margaret Seif