linux-kernel - Re: [PATCH 19/21] gpio: swnode: replace gpiochip_find() with gpio_device_find_by

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Message-ID: <26455575da695f26570392a333e7466a01a338e5.camel@crapouillou.net>
Date: Wed, 24 Jan 2024 16:11:31 +0100
From: Paul Cercueil <paul@...pouillou.net>
To: Bartosz Golaszewski <brgl@...ev.pl>
Cc: Aaro Koskinen <aaro.koskinen@....fi>, Janusz Krzysztofik
 <jmkrzyszt@...il.com>, Tony Lindgren <tony@...mide.com>, Russell King
 <linux@...linux.org.uk>, Mika Westerberg <mika.westerberg@...ux.intel.com>,
  Andy Shevchenko <andriy.shevchenko@...ux.intel.com>, Linus Walleij
 <linus.walleij@...aro.org>, Dipen Patel <dipenp@...dia.com>, Thierry Reding
 <thierry.reding@...il.com>, Jonathan Hunter <jonathanh@...dia.com>, Hans de
 Goede <hdegoede@...hat.com>, Mark Gross <markgross@...nel.org>,
 linux-arm-kernel@...ts.infradead.org,  linux-omap@...r.kernel.org,
 linux-kernel@...r.kernel.org,  linux-gpio@...r.kernel.org,
 linux-acpi@...r.kernel.org,  timestamp@...ts.linux.dev,
 linux-tegra@...r.kernel.org,  platform-driver-x86@...r.kernel.org, Bartosz
 Golaszewski <bartosz.golaszewski@...aro.org>
Subject: Re: [PATCH 19/21] gpio: swnode: replace gpiochip_find() with
 gpio_device_find_by_label()

Le mercredi 24 janvier 2024 à 16:04 +0100, Bartosz Golaszewski a
écrit :
> On Wed, Jan 24, 2024 at 3:59 PM Paul Cercueil <paul@...pouillou.net>
> wrote:
> > 
> > Hi Bartosz,
> > 
> > Le mardi 05 septembre 2023 à 20:53 +0200, Bartosz Golaszewski a
> > écrit :
> > > From: Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
> > > 
> > > We're porting all users of gpiochip_find() to using
> > > gpio_device_find().
> > > Update the swnode GPIO code.
> > > 
> > > Signed-off-by: Bartosz Golaszewski
> > > <bartosz.golaszewski@...aro.org>
> > > ---
> > >  drivers/gpio/gpiolib-swnode.c | 29 ++++++++++++-----------------
> > >  1 file changed, 12 insertions(+), 17 deletions(-)
> > > 
> > > diff --git a/drivers/gpio/gpiolib-swnode.c
> > > b/drivers/gpio/gpiolib-
> > > swnode.c
> > > index b5a6eaf3729b..56c8519be538 100644
> > > --- a/drivers/gpio/gpiolib-swnode.c
> > > +++ b/drivers/gpio/gpiolib-swnode.c
> > > @@ -31,31 +31,26 @@ static void swnode_format_propname(const char
> > > *con_id, char *propname,
> > >               strscpy(propname, "gpios", max_size);
> > >  }
> > > 
> > > -static int swnode_gpiochip_match_name(struct gpio_chip *chip,
> > > void
> > > *data)
> > > +static struct gpio_device *swnode_get_gpio_device(struct
> > > fwnode_handle *fwnode)
> > >  {
> > > -     return !strcmp(chip->label, data);
> > > -}
> > > +     const struct software_node *gdev_node;
> > > +     struct gpio_device *gdev;
> > > 
> > > -static struct gpio_chip *swnode_get_chip(struct fwnode_handle
> > > *fwnode)
> > > -{
> > > -     const struct software_node *chip_node;
> > > -     struct gpio_chip *chip;
> > > -
> > > -     chip_node = to_software_node(fwnode);
> > > -     if (!chip_node || !chip_node->name)
> > > +     gdev_node = to_software_node(fwnode);
> > > +     if (!gdev_node || !gdev_node->name)
> > >               return ERR_PTR(-EINVAL);
> > > 
> > > -     chip = gpiochip_find((void *)chip_node->name,
> > > swnode_gpiochip_match_name);
> > > -     return chip ?: ERR_PTR(-EPROBE_DEFER);
> > > +     gdev = gpio_device_find_by_label((void *)gdev_node->name);
> > > +     return gdev ?: ERR_PTR(-EPROBE_DEFER);
> > >  }
> > > 
> > >  struct gpio_desc *swnode_find_gpio(struct fwnode_handle *fwnode,
> > >                                  const char *con_id, unsigned int
> > > idx,
> > >                                  unsigned long *flags)
> > >  {
> > > +     struct gpio_device *gdev __free(gpio_device_put) = NULL;
> > >       const struct software_node *swnode;
> > >       struct fwnode_reference_args args;
> > > -     struct gpio_chip *chip;
> > >       struct gpio_desc *desc;
> > >       char propname[32]; /* 32 is max size of property name */
> > >       int error;
> > > @@ -77,12 +72,12 @@ struct gpio_desc *swnode_find_gpio(struct
> > > fwnode_handle *fwnode,
> > >               return ERR_PTR(error);
> > >       }
> > > 
> > > -     chip = swnode_get_chip(args.fwnode);
> > > +     gdev = swnode_get_gpio_device(args.fwnode);
> > >       fwnode_handle_put(args.fwnode);
> > > -     if (IS_ERR(chip))
> > > -             return ERR_CAST(chip);
> > > +     if (IS_ERR(gdev))
> > > +             return ERR_CAST(gdev);
> > 
> > I'm a bit late to the party, sorry.
> > 
> > I'm looking at how __free() should be used to use it in my own
> > patchset, and I was wondering if this code actually works.
> > 
> > What happens if swnode_get_gpio_device() returns an error pointer?
> > Won't that cause a call to gpio_device_put() with the invalid
> > pointer?
> > 
> > Cheers,
> > -Paul
> > 
> 
> No. because the __free() callback is defined as:
> 
> DEFINE_FREE(gpio_device_put, struct gpio_device *,
>     if (!IS_ERR_OR_NULL(_T)) gpio_device_put(_T))

Ok. I missed this.

I would argue that it's still not right though - it should probably use
IS_ERR() instead. gpio_device_put() only happens to accept NULL
pointers because the "dev" field is at the very beginning of the
"gpio_device" struct. I'm not sure this works with e.g.
CONFIG_RANDSTRUCT_FULL.

> Bart

Cheers,
-Paul

> > > 
> > > -     desc = gpiochip_get_desc(chip, args.args[0]);
> > > +     desc = gpiochip_get_desc(gdev->chip, argsargs[0]);
> > >       *flags = args.args[1]; /* We expect native GPIO flags */
> > > 
> > >       pr_debug("%s: parsed '%s' property of node '%pfwP[%d]' -
> > > status (%d)\n",
> >