diff mbox series

[v2,08/23] gpio: sysfs: use gpio_device_find() to iterate over existing devices

Message ID 20240205093418.39755-9-brgl@bgdev.pl
State New
Headers show
Series gpio: rework locking and object life-time control | expand

Commit Message

Bartosz Golaszewski Feb. 5, 2024, 9:34 a.m. UTC
From: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>

With the list of GPIO devices now protected with SRCU we can use
gpio_device_find() to traverse it from sysfs.

Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
---
 drivers/gpio/gpiolib-sysfs.c | 41 ++++++++++++++++--------------------
 drivers/gpio/gpiolib.c       |  2 +-
 drivers/gpio/gpiolib.h       |  1 -
 3 files changed, 19 insertions(+), 25 deletions(-)

Comments

Andy Shevchenko Feb. 5, 2024, 12:18 p.m. UTC | #1
On Mon, Feb 05, 2024 at 10:34:03AM +0100, Bartosz Golaszewski wrote:
> From: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
> 
> With the list of GPIO devices now protected with SRCU we can use
> gpio_device_find() to traverse it from sysfs.

...

> +static int gpiofind_sysfs_register(struct gpio_chip *gc, void *data)
> +{
> +	struct gpio_device *gdev = gc->gpiodev;
> +	int ret;
> +
> +	if (gdev->mockdev)
> +		return 0;
> +
> +	ret = gpiochip_sysfs_register(gdev);
> +	if (ret)
> +		chip_err(gc, "failed to register the sysfs entry: %d\n", ret);

> +	return 0;

???

> +}
Bartosz Golaszewski Feb. 5, 2024, 1:19 p.m. UTC | #2
On Mon, Feb 5, 2024 at 1:36 PM Andy Shevchenko
<andriy.shevchenko@linux.intel.com> wrote:
>
> On Mon, Feb 05, 2024 at 10:34:03AM +0100, Bartosz Golaszewski wrote:
> > From: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
> >
> > With the list of GPIO devices now protected with SRCU we can use
> > gpio_device_find() to traverse it from sysfs.
>
> ...
>
> > +static int gpiofind_sysfs_register(struct gpio_chip *gc, void *data)
> > +{
> > +     struct gpio_device *gdev = gc->gpiodev;
> > +     int ret;
> > +
> > +     if (gdev->mockdev)
> > +             return 0;
> > +
> > +     ret = gpiochip_sysfs_register(gdev);
> > +     if (ret)
> > +             chip_err(gc, "failed to register the sysfs entry: %d\n", ret);
>
> > +     return 0;
>
> ???
>

Not sure what the ... and ??? mean? The commit message should have
read "... traverse it from gpiofind_sysfs_register()" I agree but the
latter?

Bart

> > +}
>
> --
> With Best Regards,
> Andy Shevchenko
>
>
Andy Shevchenko Feb. 5, 2024, 1:38 p.m. UTC | #3
On Mon, Feb 05, 2024 at 02:19:10PM +0100, Bartosz Golaszewski wrote:
> On Mon, Feb 5, 2024 at 1:36 PM Andy Shevchenko
> <andriy.shevchenko@linux.intel.com> wrote:
> > On Mon, Feb 05, 2024 at 10:34:03AM +0100, Bartosz Golaszewski wrote:
> > > From: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
> > >
> > > With the list of GPIO devices now protected with SRCU we can use
> > > gpio_device_find() to traverse it from sysfs.

...

> > > +static int gpiofind_sysfs_register(struct gpio_chip *gc, void *data)
> > > +{
> > > +     struct gpio_device *gdev = gc->gpiodev;
> > > +     int ret;
> > > +
> > > +     if (gdev->mockdev)
> > > +             return 0;
> > > +
> > > +     ret = gpiochip_sysfs_register(gdev);
> > > +     if (ret)
> > > +             chip_err(gc, "failed to register the sysfs entry: %d\n", ret);
> >
> > > +     return 0;
> >
> > ???

What the point of function to be int if you effectively ignore this by always
returning 0?

> Not sure what the ... and ??? mean? The commit message should have
> read "... traverse it from gpiofind_sysfs_register()" I agree but the
> latter?

I didn't realize this may not be obvious :-(.

> > > +}
Bartosz Golaszewski Feb. 5, 2024, 1:39 p.m. UTC | #4
On Mon, Feb 5, 2024 at 2:38 PM Andy Shevchenko
<andriy.shevchenko@linux.intel.com> wrote:
>
> On Mon, Feb 05, 2024 at 02:19:10PM +0100, Bartosz Golaszewski wrote:
> > On Mon, Feb 5, 2024 at 1:36 PM Andy Shevchenko
> > <andriy.shevchenko@linux.intel.com> wrote:
> > > On Mon, Feb 05, 2024 at 10:34:03AM +0100, Bartosz Golaszewski wrote:
> > > > From: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
> > > >
> > > > With the list of GPIO devices now protected with SRCU we can use
> > > > gpio_device_find() to traverse it from sysfs.
>
> ...
>
> > > > +static int gpiofind_sysfs_register(struct gpio_chip *gc, void *data)
> > > > +{
> > > > +     struct gpio_device *gdev = gc->gpiodev;
> > > > +     int ret;
> > > > +
> > > > +     if (gdev->mockdev)
> > > > +             return 0;
> > > > +
> > > > +     ret = gpiochip_sysfs_register(gdev);
> > > > +     if (ret)
> > > > +             chip_err(gc, "failed to register the sysfs entry: %d\n", ret);
> > >
> > > > +     return 0;
> > >
> > > ???
>
> What the point of function to be int if you effectively ignore this by always
> returning 0?
>

Because the signature of the callback expects an int to be returned?

Bart

> > Not sure what the ... and ??? mean? The commit message should have
> > read "... traverse it from gpiofind_sysfs_register()" I agree but the
> > latter?
>
> I didn't realize this may not be obvious :-(.
>
> > > > +}
>
> --
> With Best Regards,
> Andy Shevchenko
>
>
Andy Shevchenko Feb. 5, 2024, 1:47 p.m. UTC | #5
On Mon, Feb 05, 2024 at 02:39:40PM +0100, Bartosz Golaszewski wrote:
> On Mon, Feb 5, 2024 at 2:38 PM Andy Shevchenko
> <andriy.shevchenko@linux.intel.com> wrote:
> > On Mon, Feb 05, 2024 at 02:19:10PM +0100, Bartosz Golaszewski wrote:
> > > On Mon, Feb 5, 2024 at 1:36 PM Andy Shevchenko
> > > <andriy.shevchenko@linux.intel.com> wrote:
> > > > On Mon, Feb 05, 2024 at 10:34:03AM +0100, Bartosz Golaszewski wrote:

...

> > > > > +static int gpiofind_sysfs_register(struct gpio_chip *gc, void *data)
> > > > > +{
> > > > > +     struct gpio_device *gdev = gc->gpiodev;
> > > > > +     int ret;
> > > > > +
> > > > > +     if (gdev->mockdev)
> > > > > +             return 0;
> > > > > +
> > > > > +     ret = gpiochip_sysfs_register(gdev);
> > > > > +     if (ret)
> > > > > +             chip_err(gc, "failed to register the sysfs entry: %d\n", ret);
> > > >
> > > > > +     return 0;
> > > >
> > > > ???
> >
> > What the point of function to be int if you effectively ignore this by always
> > returning 0?
> >
> 
> Because the signature of the callback expects an int to be returned?

But why do you return 0 instead of ret?

> > > Not sure what the ... and ??? mean? The commit message should have
> > > read "... traverse it from gpiofind_sysfs_register()" I agree but the
> > > latter?
> >
> > I didn't realize this may not be obvious :-(.
> >
> > > > > +}
Bartosz Golaszewski Feb. 5, 2024, 1:50 p.m. UTC | #6
On Mon, Feb 5, 2024 at 2:47 PM Andy Shevchenko
<andriy.shevchenko@linux.intel.com> wrote:
>
> On Mon, Feb 05, 2024 at 02:39:40PM +0100, Bartosz Golaszewski wrote:
> > On Mon, Feb 5, 2024 at 2:38 PM Andy Shevchenko
> > <andriy.shevchenko@linux.intel.com> wrote:
> > > On Mon, Feb 05, 2024 at 02:19:10PM +0100, Bartosz Golaszewski wrote:
> > > > On Mon, Feb 5, 2024 at 1:36 PM Andy Shevchenko
> > > > <andriy.shevchenko@linux.intel.com> wrote:
> > > > > On Mon, Feb 05, 2024 at 10:34:03AM +0100, Bartosz Golaszewski wrote:
>
> ...
>
> > > > > > +static int gpiofind_sysfs_register(struct gpio_chip *gc, void *data)
> > > > > > +{
> > > > > > +     struct gpio_device *gdev = gc->gpiodev;
> > > > > > +     int ret;
> > > > > > +
> > > > > > +     if (gdev->mockdev)
> > > > > > +             return 0;
> > > > > > +
> > > > > > +     ret = gpiochip_sysfs_register(gdev);
> > > > > > +     if (ret)
> > > > > > +             chip_err(gc, "failed to register the sysfs entry: %d\n", ret);
> > > > >
> > > > > > +     return 0;
> > > > >
> > > > > ???
> > >
> > > What the point of function to be int if you effectively ignore this by always
> > > returning 0?
> > >
> >
> > Because the signature of the callback expects an int to be returned?
>
> But why do you return 0 instead of ret?
>

Because we don't want to *find* a device really. We just want to
iterate over all of them and call a callback. Any value other than 0
will be interpreted as a match. Besides: failure to register one GPIO
sysfs entry shouldn't maybe cause a failure for all subsequent
devices?

Bart

> > > > Not sure what the ... and ??? mean? The commit message should have
> > > > read "... traverse it from gpiofind_sysfs_register()" I agree but the
> > > > latter?
> > >
> > > I didn't realize this may not be obvious :-(.
> > >
> > > > > > +}
>
> --
> With Best Regards,
> Andy Shevchenko
>
>
Andy Shevchenko Feb. 5, 2024, 1:58 p.m. UTC | #7
On Mon, Feb 05, 2024 at 02:50:18PM +0100, Bartosz Golaszewski wrote:
> On Mon, Feb 5, 2024 at 2:47 PM Andy Shevchenko
> <andriy.shevchenko@linux.intel.com> wrote:
> > On Mon, Feb 05, 2024 at 02:39:40PM +0100, Bartosz Golaszewski wrote:
> > > On Mon, Feb 5, 2024 at 2:38 PM Andy Shevchenko
> > > <andriy.shevchenko@linux.intel.com> wrote:
> > > > On Mon, Feb 05, 2024 at 02:19:10PM +0100, Bartosz Golaszewski wrote:
> > > > > On Mon, Feb 5, 2024 at 1:36 PM Andy Shevchenko
> > > > > <andriy.shevchenko@linux.intel.com> wrote:
> > > > > > On Mon, Feb 05, 2024 at 10:34:03AM +0100, Bartosz Golaszewski wrote:

...

> > > > > > > +static int gpiofind_sysfs_register(struct gpio_chip *gc, void *data)
> > > > > > > +{
> > > > > > > +     struct gpio_device *gdev = gc->gpiodev;
> > > > > > > +     int ret;
> > > > > > > +
> > > > > > > +     if (gdev->mockdev)
> > > > > > > +             return 0;
> > > > > > > +
> > > > > > > +     ret = gpiochip_sysfs_register(gdev);
> > > > > > > +     if (ret)
> > > > > > > +             chip_err(gc, "failed to register the sysfs entry: %d\n", ret);
> > > > > >
> > > > > > > +     return 0;
> > > > > >
> > > > > > ???
> > > >
> > > > What the point of function to be int if you effectively ignore this by always
> > > > returning 0?
> > >
> > > Because the signature of the callback expects an int to be returned?
> >
> > But why do you return 0 instead of ret?
> >
> 
> Because we don't want to *find* a device really. We just want to
> iterate over all of them and call a callback. Any value other than 0
> will be interpreted as a match. Besides: failure to register one GPIO
> sysfs entry shouldn't maybe cause a failure for all subsequent
> devices?

To me it's not obvious, hence I would like to see a comment before return 0.

> > > > > Not sure what the ... and ??? mean? The commit message should have
> > > > > read "... traverse it from gpiofind_sysfs_register()" I agree but the
> > > > > latter?
> > > >
> > > > I didn't realize this may not be obvious :-(.
> > > >
> > > > > > > +}
Bartosz Golaszewski Feb. 5, 2024, 2:04 p.m. UTC | #8
On Mon, Feb 5, 2024 at 2:59 PM Andy Shevchenko
<andriy.shevchenko@linux.intel.com> wrote:
>
> On Mon, Feb 05, 2024 at 02:50:18PM +0100, Bartosz Golaszewski wrote:
> > On Mon, Feb 5, 2024 at 2:47 PM Andy Shevchenko
> > <andriy.shevchenko@linux.intel.com> wrote:
> > > On Mon, Feb 05, 2024 at 02:39:40PM +0100, Bartosz Golaszewski wrote:
> > > > On Mon, Feb 5, 2024 at 2:38 PM Andy Shevchenko
> > > > <andriy.shevchenko@linux.intel.com> wrote:
> > > > > On Mon, Feb 05, 2024 at 02:19:10PM +0100, Bartosz Golaszewski wrote:
> > > > > > On Mon, Feb 5, 2024 at 1:36 PM Andy Shevchenko
> > > > > > <andriy.shevchenko@linux.intel.com> wrote:
> > > > > > > On Mon, Feb 05, 2024 at 10:34:03AM +0100, Bartosz Golaszewski wrote:
>
> ...
>
> > > > > > > > +static int gpiofind_sysfs_register(struct gpio_chip *gc, void *data)
> > > > > > > > +{
> > > > > > > > +     struct gpio_device *gdev = gc->gpiodev;
> > > > > > > > +     int ret;
> > > > > > > > +
> > > > > > > > +     if (gdev->mockdev)
> > > > > > > > +             return 0;
> > > > > > > > +
> > > > > > > > +     ret = gpiochip_sysfs_register(gdev);
> > > > > > > > +     if (ret)
> > > > > > > > +             chip_err(gc, "failed to register the sysfs entry: %d\n", ret);
> > > > > > >
> > > > > > > > +     return 0;
> > > > > > >
> > > > > > > ???
> > > > >
> > > > > What the point of function to be int if you effectively ignore this by always
> > > > > returning 0?
> > > >
> > > > Because the signature of the callback expects an int to be returned?
> > >
> > > But why do you return 0 instead of ret?
> > >
> >
> > Because we don't want to *find* a device really. We just want to
> > iterate over all of them and call a callback. Any value other than 0
> > will be interpreted as a match. Besides: failure to register one GPIO
> > sysfs entry shouldn't maybe cause a failure for all subsequent
> > devices?
>
> To me it's not obvious, hence I would like to see a comment before return 0.
>

I'll add it for v3.

Bart

> > > > > > Not sure what the ... and ??? mean? The commit message should have
> > > > > > read "... traverse it from gpiofind_sysfs_register()" I agree but the
> > > > > > latter?
> > > > >
> > > > > I didn't realize this may not be obvious :-(.
> > > > >
> > > > > > > > +}
>
> --
> With Best Regards,
> Andy Shevchenko
>
>
diff mbox series

Patch

diff --git a/drivers/gpio/gpiolib-sysfs.c b/drivers/gpio/gpiolib-sysfs.c
index 6bf5332136e5..3c3b8559cff5 100644
--- a/drivers/gpio/gpiolib-sysfs.c
+++ b/drivers/gpio/gpiolib-sysfs.c
@@ -790,11 +790,24 @@  void gpiochip_sysfs_unregister(struct gpio_device *gdev)
 	}
 }
 
+static int gpiofind_sysfs_register(struct gpio_chip *gc, void *data)
+{
+	struct gpio_device *gdev = gc->gpiodev;
+	int ret;
+
+	if (gdev->mockdev)
+		return 0;
+
+	ret = gpiochip_sysfs_register(gdev);
+	if (ret)
+		chip_err(gc, "failed to register the sysfs entry: %d\n", ret);
+
+	return 0;
+}
+
 static int __init gpiolib_sysfs_init(void)
 {
-	int		status;
-	unsigned long	flags;
-	struct gpio_device *gdev;
+	int status;
 
 	status = class_register(&gpio_class);
 	if (status < 0)
@@ -806,26 +819,8 @@  static int __init gpiolib_sysfs_init(void)
 	 * We run before arch_initcall() so chip->dev nodes can have
 	 * registered, and so arch_initcall() can always gpiod_export().
 	 */
-	spin_lock_irqsave(&gpio_lock, flags);
-	list_for_each_entry(gdev, &gpio_devices, list) {
-		if (gdev->mockdev)
-			continue;
+	gpio_device_find(NULL, gpiofind_sysfs_register);
 
-		/*
-		 * TODO we yield gpio_lock here because
-		 * gpiochip_sysfs_register() acquires a mutex. This is unsafe
-		 * and needs to be fixed.
-		 *
-		 * Also it would be nice to use gpio_device_find() here so we
-		 * can keep gpio_chips local to gpiolib.c, but the yield of
-		 * gpio_lock prevents us from doing this.
-		 */
-		spin_unlock_irqrestore(&gpio_lock, flags);
-		status = gpiochip_sysfs_register(gdev);
-		spin_lock_irqsave(&gpio_lock, flags);
-	}
-	spin_unlock_irqrestore(&gpio_lock, flags);
-
-	return status;
+	return 0;
 }
 postcore_initcall(gpiolib_sysfs_init);
diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index f425e0264b7e..6cfb75ee739d 100644
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -85,7 +85,7 @@  DEFINE_SPINLOCK(gpio_lock);
 static DEFINE_MUTEX(gpio_lookup_lock);
 static LIST_HEAD(gpio_lookup_list);
 
-LIST_HEAD(gpio_devices);
+static LIST_HEAD(gpio_devices);
 /* Protects the GPIO device list against concurrent modifications. */
 static DEFINE_MUTEX(gpio_devices_lock);
 /* Ensures coherence during read-only accesses to the list of GPIO devices. */
diff --git a/drivers/gpio/gpiolib.h b/drivers/gpio/gpiolib.h
index d2e73eea9e92..2bf3f9e13ae4 100644
--- a/drivers/gpio/gpiolib.h
+++ b/drivers/gpio/gpiolib.h
@@ -136,7 +136,6 @@  int gpiod_set_array_value_complex(bool raw, bool can_sleep,
 int gpiod_set_transitory(struct gpio_desc *desc, bool transitory);
 
 extern spinlock_t gpio_lock;
-extern struct list_head gpio_devices;
 
 void gpiod_line_state_notify(struct gpio_desc *desc, unsigned long action);