linux-kernel - Re: [PATCH stable] gpiolib: Read "gpio-line-names" from a firmware node

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Date:   Sat, 10 Apr 2021 15:23:31 +0200
From:   Bartosz Golaszewski <brgl@...ev.pl>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     "open list:GPIO SUBSYSTEM" <linux-gpio@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        stable <stable@...r.kernel.org>, Marek Vasut <marex@...x.de>,
        Roman Guskov <rguskov@...electronics.com>,
        Bartosz Golaszewski <bgolaszewski@...libre.com>
Subject: Re: [PATCH stable] gpiolib: Read "gpio-line-names" from a firmware node

On Sat, Apr 10, 2021 at 2:07 PM Greg Kroah-Hartman
<gregkh@...uxfoundation.org> wrote:
>
> On Sat, Apr 10, 2021 at 11:09:19AM +0200, Bartosz Golaszewski wrote:
> > From: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
> >
> > On STM32MP1, the GPIO banks are subnodes of pin-controller@...02000,
> > see arch/arm/boot/dts/stm32mp151.dtsi. The driver for
> > pin-controller@...02000 is in drivers/pinctrl/stm32/pinctrl-stm32.c
> > and iterates over all of its DT subnodes when registering each GPIO
> > bank gpiochip. Each gpiochip has:
> >
> >   - gpio_chip.parent = dev,
> >     where dev is the device node of the pin controller
> >   - gpio_chip.of_node = np,
> >     which is the OF node of the GPIO bank
> >
> > Therefore, dev_fwnode(chip->parent) != of_fwnode_handle(chip.of_node),
> > i.e. pin-controller@...02000 != pin-controller@...02000/gpio@...0*000.
> >
> > The original code behaved correctly, as it extracted the "gpio-line-names"
> > from of_fwnode_handle(chip.of_node) = pin-controller@...02000/gpio@...0*000.
> >
> > To achieve the same behaviour, read property from the firmware node.
> >
> > Fixes: 7cba1a4d5e162 ("gpiolib: generalize devprop_gpiochip_set_names() for device properties")
> > Cc: stable@...r.kernel.org
> > Reported-by: Marek Vasut <marex@...x.de>
> > Reported-by: Roman Guskov <rguskov@...electronics.com>
> > Signed-off-by: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
> > Tested-by: Marek Vasut <marex@...x.de>
> > Reviewed-by: Marek Vasut <marex@...x.de>
> > Signed-off-by: Bartosz Golaszewski <bgolaszewski@...libre.com>
> > ---
> > Hi Greg,
> >
> > This patch somehow got lost and never made its way into stable. Could you
> > please apply it?
>
> This has been added and removed more times than I can remember already.
>
> Are you all _SURE_ this is safe for a stable kernel release?  Look in
> the archives for complaints when we added this in the past.
>
> thanks,
>
> greg k-h

IIRC it fixed the stm32mp1 problem but exposed a different problem
breaking other users until Andy fixed the deeper issue elsewhere.

It's now fine to apply it.

Bartosz