Re: [PATCH] pinctrl: bcm2835: Make pin freeing behavior configurable

From: Kent Gibson <warthog618@gmail.com>
To: Stefan Wahren <wahrenst@gmx.net>
Cc: Linus Walleij <linus.walleij@linaro.org>,
	Florian Fainelli <florian.fainelli@broadcom.com>,
	bcm-kernel-feedback-list@broadcom.com,
	Ray Jui <rjui@broadcom.com>,
	Scott Branden <sbranden@broadcom.com>,
	linux-gpio@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
	Bartosz Golaszewski <brgl@bgdev.pl>,
	Phil Elwell <phil@raspberrypi.com>
Subject: Re: [PATCH] pinctrl: bcm2835: Make pin freeing behavior configurable
Date: Thu, 2 May 2024 19:15:46 +0800	[thread overview]
Message-ID: <20240502111546.GA325017@rigel> (raw)
In-Reply-To: <79627aeb-8151-430c-98f4-5689fd61413f@gmx.net>

On Thu, May 02, 2024 at 01:11:06PM +0200, Stefan Wahren wrote:
> Hi Kent,
>
> Am 02.05.24 um 13:04 schrieb Kent Gibson:
> > On Thu, May 02, 2024 at 12:22:07PM +0200, Stefan Wahren wrote:
> > > Am 19.04.24 um 22:40 schrieb Stefan Wahren:
> > > > Until now after a bcm2835 pin was freed its pinmux was set to GPIO_IN.
> > > > So in case it was configured as GPIO_OUT before the configured output
> > > > level also get lost. As long as GPIO sysfs was used this wasn't
> > > > actually a problem because the pins and their possible output level
> > > > were kept by sysfs.
> > > >
> > > > Since more and more Raspberry Pi users start using libgpiod they are
> > > > confused about this behavior. So make the pin freeing behavior of
> > > > GPIO_OUT configurable via module parameter. In case
> > > > pinctrl-bcm2835.strict_gpiod is set to 0, the output level is kept.
> > > >
> > > > This patch based on the downstream work of Phil Elwell.
> > > >
> > > > Link: https://github.com/raspberrypi/linux/pull/6117
> > > > Signed-off-by: Stefan Wahren <wahrenst@gmx.net>
> > > > ---
> > > >    drivers/pinctrl/bcm/pinctrl-bcm2835.c | 20 ++++++++++++++++----
> > > >    1 file changed, 16 insertions(+), 4 deletions(-)
> > > Gentle ping ...
> > I can't comment on the substance of the change as pinctrl is outside my
> > wheelhouse, but the "strict_gpiod" name could be better.
> > The point is to make GPIO outputs persist, right?
> Yes, correct.
> > The name should better reflect that.
> Finding good and short names is hard, do you have a suggestion?
>

How about "persist_gpio_outputs"?

Cheers,
Kent.