From: Rob Herring <robh+dt@kernel.org>
To: Peter Ujfalusi <peter.ujfalusi@ti.com>
Cc: Mark Brown <broonie@kernel.org>,
Linus Walleij <linus.walleij@linaro.org>,
Bartosz Golaszewski <bgolaszewski@baylibre.com>,
"open list:GPIO SUBSYSTEM" <linux-gpio@vger.kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
Marek Szyprowski <m.szyprowski@samsung.com>,
Tero Kristo <t-kristo@ti.com>, Maxime Ripard <mripard@kernel.org>,
Philipp Zabel <p.zabel@pengutronix.de>,
devicetree@vger.kernel.org
Subject: Re: [RFC v2 0/2] gpio: Support for shared GPIO lines on boards
Date: Wed, 30 Oct 2019 13:49:25 -0500 [thread overview]
Message-ID: <CAL_JsqJ4WdaRvmZcjQG-jVyOOeKZX9fn1WcQZGWfUPqwunQCFw@mail.gmail.com> (raw)
In-Reply-To: <f9c181d1-5e0c-5e82-a740-f4e97822604f@ti.com>
On Wed, Oct 30, 2019 at 9:30 AM Peter Ujfalusi <peter.ujfalusi@ti.com> wrote:
>
>
>
> On 30/10/2019 16.17, Mark Brown wrote:
> > On Wed, Oct 30, 2019 at 03:32:09PM +0200, Peter Ujfalusi wrote:
> >> On 30/10/2019 15.12, Rob Herring wrote:
> >
> >>> Why can't we just add a shared flag like we have for interrupts?
> >>> Effectively, we have that for resets too, it's just hardcoded in the
> >>> the drivers.
> >
> >> This would be kind of the same thing what the
> >> GPIOD_FLAGS_BIT_NONEXCLUSIVE does, which was a quick workaround for
> >> fixed-regulators afaik.
> >
> > The theory with that was that any usage of this would need the
> > higher level code using the GPIO to cooperate so they didn't step
> > on each other's toes so the GPIO code should just punt to it.
>
> But from the client driver point of view a GPIO is still GPIO and if the
> components are unrelated then it is hard to patch things together from
> the top.
You can't escape a driver being aware. If a driver depends on that
GPIO to actually be set to states the driver says, then it can't be
guaranteed to work. For example, maybe the driver assumes the device
is in reset state after toggling reset and doesn't work if not in
reset state. The driver has to be aware no matter what you do in DT.
Rob
next prev parent reply other threads:[~2019-10-30 18:49 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-10-30 12:04 [RFC v2 0/2] gpio: Support for shared GPIO lines on boards Peter Ujfalusi
2019-10-30 12:04 ` [RFC v2 1/2] dt-bindings: gpio: Add binding document for shared GPIO Peter Ujfalusi
2019-10-30 12:04 ` [RFC v2 2/2] gpio: Add new driver for handling 'shared' gpio lines on boards Peter Ujfalusi
2019-10-30 13:12 ` [RFC v2 0/2] gpio: Support for shared GPIO " Rob Herring
2019-10-30 13:32 ` Peter Ujfalusi
2019-10-30 13:51 ` Philipp Zabel
2019-10-30 14:03 ` Peter Ujfalusi
2019-10-30 14:17 ` Mark Brown
2019-10-30 14:31 ` Peter Ujfalusi
2019-10-30 18:49 ` Rob Herring [this message]
2019-10-31 8:01 ` Peter Ujfalusi
2019-11-01 13:46 ` Rob Herring
2019-11-01 15:21 ` Peter Ujfalusi
2019-11-04 19:11 ` Rob Herring
2019-11-05 9:58 ` Linus Walleij
2019-11-05 11:15 ` Peter Ujfalusi
2019-11-05 12:15 ` Grygorii Strashko
2019-11-05 12:32 ` Peter Ujfalusi
2019-11-05 18:07 ` Grygorii Strashko
2019-11-06 9:23 ` Peter Ujfalusi
2019-11-06 10:00 ` Philipp Zabel
2019-11-05 12:17 ` Peter Ujfalusi
2019-11-18 12:15 ` Enrico Weigelt, metux IT consult
2019-11-18 13:38 ` Philipp Zabel
2019-11-18 14:00 ` Peter Ujfalusi
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