linux-kernel - Re: [Patch v6 0/2] gpio: add GPIO hogging mechanism

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Date:	Thu, 19 Feb 2015 15:46:39 -0600
From:	Michael Welling <mwelling@...e.org>
To:	Benoit Parrot <bparrot@...com>
Cc:	Linus Walleij <linus.walleij@...aro.org>,
	linux-gpio@...r.kernel.org, linux-kernel@...r.kernel.org,
	devicetree@...r.kernel.org, Alexandre Courbot <gnurou@...il.com>,
	Maxime Ripard <maxime.ripard@...e-electrons.com>,
	Jiri Prchal <jiri.prchal@...ignal.cz>,
	Pantelis Antoniou <panto@...oniou-consulting.com>
Subject: Re: [Patch v6 0/2] gpio: add GPIO hogging mechanism

On Wed, Feb 18, 2015 at 11:23:42AM -0600, Benoit Parrot wrote:
> Gentle ping.
> 
> Is there any chance this will make it in 3.21?
> 
> Benoit
>

Is there a reason that the pin has to be "hogged"?

Couldn't the pin be released after configuration for eventual use in the userspace?
 
> Parrot, Benoit <bparrot@...com> wrote on Wed [2015-Feb-02 17:44:43 -0600]:
> > This patch set re-introduces the gpio hogging concept first
> > presented by Boris Brezillion.
> > This patch set provides a way to initially configure specific GPIO
> > when the GPIO controller is probed.
> >  
> > The actual DT scanning to collect the GPIO specific data is performed
> > as part of of_gpiochip_add().
> >  
> > The purpose of this is to allow specific GPIOs to be configured
> > without any driver specific code.
> > This is particularly useful because board design are getting
> > increasingly complex and given SoC pins can now have more
> > than 10 mux values a lot of connections are now dependent on
> > external IO muxes to switch various modes.
> >  
> > Specific drivers should not necessarily need to be aware of
> > what accounts to a specific board implementation. This board level
> > "description" should be best kept as part of the dts file.
> >  
> > Changes since v5:
> > * Addressed review comment from Linus Walleij
> > * Replace "state" property back with separate boolean properties
> > * Renamed helper function
> > * Refactored pr_* calls to remove "__func__"
> >  
> > Changes since v4:
> > * Addressed review comments from Alexandre Courbot
> >  
> > Changes since v3:
> > * Relocated the non-DT "hog" function to gpiolib.c.
> > * Rename some of the function to be clearer and remove _ prefixes.
> > * Replace the gpiod_request/gpiod_put usage with
> >    gpiochip_request_own_desc/free_own_desc version instead.
> > * Refactor some of the logic to better handle error condition/reporting
> > * Renamed the "direction" DT properties to "state".
> >  
> > Changes since v2:
> > * Refactor the gpio-hog mechanism to split the DT related action
> >    from the actual "hogging" operation.
> > * This allows non-DT providers to implement hogs as well.
> > * Added FLAG_IS_HOGGED to mark hogged gpio and make gpiochip removal
> >    able to release hogged gpio.
> > * Similarly to the hogging, the cleanup is performed as part of
> >    of_gpiochip_remove
> >  
> > Changes since v1:
> > * Split the devicetree bindings documentation in its own patch.
> > * Refactor the gpio-hog mechanism as private functions meant to
> >    be to invoked from of_gpiochip_add().
> >  
> >  
> > Benoit Parrot (2):
> >   gpio: add GPIO hogging mechanism
> >   gpio: Document GPIO hogging mechanism
> >  
> > Documentation/devicetree/bindings/gpio/gpio.txt |  30 ++++++
> > drivers/gpio/gpiolib-of.c                       | 111 +++++++++++++++++++++
> > drivers/gpio/gpiolib.c                          | 124 ++++++++++++++++++++----
> > drivers/gpio/gpiolib.h                          |   3 +
> > 4 files changed, 249 insertions(+), 19 deletions(-)
> >  
> > --
> > 1.8.5.1
> >  
> > --
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> >  
> > 
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