From mboxrd@z Thu Jan  1 00:00:00 1970
From: thomas.petazzoni@free-electrons.com (Thomas Petazzoni)
Date: Wed, 30 Aug 2017 16:32:55 +0200
Subject: linux-next regression caused by "gpiolib: request the gpio
 before querying its direction"
In-Reply-To: <442accaa-15a0-4efb-4e5c-cebca7140213@codeaurora.org>
References: <20170830112424.7a3a7c36@windsurf.lan>
 <3cce6903-d167-1bfc-38b4-1fdd7b3ff24b@codeaurora.org>
 <87ziah2m3f.fsf@free-electrons.com>
 <20170830161730.41919554@windsurf.lan>
 <442accaa-15a0-4efb-4e5c-cebca7140213@codeaurora.org>
Message-ID: <20170830163255.4e7c1422@windsurf.lan>
To: linux-arm-kernel@lists.infradead.org
List-Id: linux-arm-kernel.lists.infradead.org

Hello,

On Wed, 30 Aug 2017 09:22:55 -0500, Timur Tabi wrote:

> No, that's it.  The question is, what exactly should the 'request' 
> function do?  Should it be modifying the hardware to satisfy the 
> request?  When I wrote my patch, I assumed that it wouldn't.  I thought 
> that request simply answered the question, "can I touch this GPIO"?

No, it also muxes the pin in GPIO, and you can see the "reference"
implementation pinctrl-single also does it.

Let's see what Linus W. has to say about the semantic of the "request"
operation.

But if we change the semantic of "request" to no longer mux the hardware
as GPIO, then you will also have regressions, because there are plenty
of GPIOs that are requested, but not explicitly muxed as GPIOs in the
DT, precisely because today requesting a GPIO is sufficient to have it
re-muxed as GPIO at the pinctrl level.

Best regards,

Thomas
-- 
Thomas Petazzoni, CTO, Free Electrons
Embedded Linux and Kernel engineering
http://free-electrons.com