linux-kernel - Re: [PATCH v6 2/4] pps: descriptor-based gpio, capture-clear addition

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Date:   Sat, 17 Nov 2018 12:11:10 +0100
From:   Philipp Zabel <philipp.zabel@...il.com>
To:     tom@...sec.com
Cc:     LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v6 2/4] pps: descriptor-based gpio, capture-clear addition

Hi Tom,

On Tue, Nov 13, 2018 at 5:08 AM Tom Burkart <tom@...sec.com> wrote:
>
> This patch changes the GPIO access for the pps-gpio driver from the
> integer based API to the descriptor based API.  It also adds
> documentation for the device tree capture-clear option and
> device tree capture-clear extraction.
>
> The change from integer based GPIO API to the descriptor based API
> breaks backward compatibility for the devicetree.  This is due to
> the descriptor based API appending "-gpio" or "-gpios" (see
> Documentation/gpio/base.txt.)

Documentation/devicetree/bindings/gpio/gpio.txt says:
 "While a non-existent <name> is considered valid
  for compatibility reasons (resolving to the "gpios" property),
  it is not allowed for new bindings."

This is not a new binding, so there should be no reason to change it.

gpiod_get() and friends support this by using the "gpios" property if
they are passed a NULL con_id.
of_find_gpio() in drivers/gpio/gpiolib-of.c contains the relevant code.

regards
Philipp