linux-kernel - Re: [PATCH v2 07/14] gpiolib: Export symbol gpiochip_set

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Message-ID: <CAMRc=MePbYdanhMH4FfHN4PRXT2HAcVyCgKndfthi0hJiSxo8Q@mail.gmail.com>
Date: Mon, 7 Oct 2024 14:51:25 +0200
From: Bartosz Golaszewski <brgl@...ev.pl>
To: Andrea della Porta <andrea.porta@...e.com>
Cc: Michael Turquette <mturquette@...libre.com>, Stephen Boyd <sboyd@...nel.org>, 
	Rob Herring <robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley <conor+dt@...nel.org>, 
	Florian Fainelli <florian.fainelli@...adcom.com>, 
	Broadcom internal kernel review list <bcm-kernel-feedback-list@...adcom.com>, 
	Lorenzo Pieralisi <lpieralisi@...nel.org>, Krzysztof Wilczyński <kw@...ux.com>, 
	Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>, Bjorn Helgaas <bhelgaas@...gle.com>, 
	Linus Walleij <linus.walleij@...aro.org>, Catalin Marinas <catalin.marinas@....com>, 
	Will Deacon <will@...nel.org>, Derek Kiernan <derek.kiernan@....com>, 
	Dragan Cvetic <dragan.cvetic@....com>, Arnd Bergmann <arnd@...db.de>, 
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>, Saravana Kannan <saravanak@...gle.com>, 
	linux-clk@...r.kernel.org, devicetree@...r.kernel.org, 
	linux-rpi-kernel@...ts.infradead.org, linux-arm-kernel@...ts.infradead.org, 
	linux-kernel@...r.kernel.org, linux-pci@...r.kernel.org, 
	linux-gpio@...r.kernel.org, Masahiro Yamada <masahiroy@...nel.org>, 
	Stefan Wahren <wahrenst@....net>, Herve Codina <herve.codina@...tlin.com>, 
	Luca Ceresoli <luca.ceresoli@...tlin.com>, Thomas Petazzoni <thomas.petazzoni@...tlin.com>, 
	Andrew Lunn <andrew@...n.ch>
Subject: Re: [PATCH v2 07/14] gpiolib: Export symbol gpiochip_set_names()

On Mon, Oct 7, 2024 at 2:39 PM Andrea della Porta <andrea.porta@...e.com> wrote:
>
> Being able to assign gpio line names dynamically is a feature
> that could be used by drivers that do not have the exact naming
> (e.g. through the DTB/DTBO) at probing time.
> An example of this is the RP1 driver that populates the DT
> at late time through a DT overlay. In this case a custom overlay
> can be loaded from userspace with the gpio line names.
>
> Export gpiochip_set_names() to allow refreshing the gpio line
> names from the driver module.
>
> Signed-off-by: Andrea della Porta <andrea.porta@...e.com>
> ---
>  drivers/gpio/gpiolib.c      | 3 ++-
>  include/linux/gpio/driver.h | 3 +++
>  2 files changed, 5 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
> index c6afbf434366..a2aa3560094a 100644
> --- a/drivers/gpio/gpiolib.c
> +++ b/drivers/gpio/gpiolib.c
> @@ -522,7 +522,7 @@ static void gpiochip_set_desc_names(struct gpio_chip *gc)
>   * names belong to the underlying firmware node and should not be released
>   * by the caller.
>   */
> -static int gpiochip_set_names(struct gpio_chip *chip)
> +int gpiochip_set_names(struct gpio_chip *chip)
>  {
>         struct gpio_device *gdev = chip->gpiodev;
>         struct device *dev = &gdev->dev;
> @@ -589,6 +589,7 @@ static int gpiochip_set_names(struct gpio_chip *chip)
>
>         return 0;
>  }
> +EXPORT_SYMBOL(gpiochip_set_names);
>
>  static unsigned long *gpiochip_allocate_mask(struct gpio_chip *gc)
>  {
> diff --git a/include/linux/gpio/driver.h b/include/linux/gpio/driver.h
> index 2dd7cb9cc270..6e4cd7b7e47e 100644
> --- a/include/linux/gpio/driver.h
> +++ b/include/linux/gpio/driver.h
> @@ -679,6 +679,9 @@ bool gpiochip_line_is_open_source(struct gpio_chip *gc, unsigned int offset);
>  bool gpiochip_line_is_persistent(struct gpio_chip *gc, unsigned int offset);
>  bool gpiochip_line_is_valid(const struct gpio_chip *gc, unsigned int offset);
>
> +/* Assign gpio line names from device property */
> +int gpiochip_set_names(struct gpio_chip *chip);
> +
>  /* get driver data */
>  void *gpiochip_get_data(struct gpio_chip *gc);
>
> --
> 2.35.3
>

gpiochip_set_names() is definitely not ready to be used after a GPIO
chip has been registered. Please take a look at how we handle
synchronization of struct gpio_device and struct gpio_desc. You'd
probably need to rework that first.

Bartosz