On 03/11/2016 05:37 PM, Linus Walleij wrote:

On Mon, Mar 7, 2016 at 7:34 PM, Michael Hennerich
[off-list ref] wrote:

quoted

On 03/05/2016 03:32 PM, Jonathan Cameron wrote:

quoted

quoted

quoted

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

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