diff mbox series

[02/21] gpiolib: provide gpio_device_find()

Message ID 20230905185309.131295-3-brgl@bgdev.pl (mailing list archive)
State New, archived
Headers show
Series gpio: convert users to gpio_device_find() and remove gpiochip_find() | expand

Commit Message

Bartosz Golaszewski Sept. 5, 2023, 6:52 p.m. UTC
From: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>

gpiochip_find() is wrong and its kernel doc is misleading as the
function doesn't return a reference to the gpio_chip but just a raw
pointer. The chip itself is not guaranteed to stay alive, in fact it can
be deleted at any point. Also: other than GPIO drivers themselves,
nobody else has any business accessing gpio_chip structs.

Provide a new gpio_device_find() function that returns a real reference
to the opaque gpio_device structure that is guaranteed to stay alive for
as long as there are active users of it.

Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
---
 drivers/gpio/gpiolib.c      | 64 ++++++++++++++++++++++++++-----------
 include/linux/gpio/driver.h |  4 +++
 2 files changed, 50 insertions(+), 18 deletions(-)

Comments

Andy Shevchenko Sept. 6, 2023, 2:10 p.m. UTC | #1
On Tue, Sep 05, 2023 at 08:52:50PM +0200, Bartosz Golaszewski wrote:
> From: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
> 
> gpiochip_find() is wrong and its kernel doc is misleading as the
> function doesn't return a reference to the gpio_chip but just a raw
> pointer. The chip itself is not guaranteed to stay alive, in fact it can
> be deleted at any point. Also: other than GPIO drivers themselves,
> nobody else has any business accessing gpio_chip structs.
> 
> Provide a new gpio_device_find() function that returns a real reference
> to the opaque gpio_device structure that is guaranteed to stay alive for
> as long as there are active users of it.

...

> +/**
> + * gpio_device_find() - find a specific GPIO device
> + * @data: data to pass to match function
> + * @match: Callback function to check gpio_chip

> + * Returns:
> + * New reference to struct gpio_device.

I believe this is wrong location of the Return section.
AFAIU how kernel doc uses section markers, this entire description becomes
a Return(s) section. Have you tried to render man/html/pdf and see this?

> + * Similar to bus_find_device(). It returns a reference to a gpio_device as
> + * determined by a user supplied @match callback. The callback should return
> + * 0 if the device doesn't match and non-zero if it does. If the callback
> + * returns non-zero, this function will return to the caller and not iterate
> + * over any more gpio_devices.
> + *
> + * The callback takes the GPIO chip structure as argument. During the execution
> + * of the callback function the chip is protected from being freed. TODO: This
> + * actually has yet to be implemented.
> + *
> + * If the function returns non-NULL, the returned reference must be freed by
> + * the caller using gpio_device_put().
> + */
> +struct gpio_device *gpio_device_find(void *data,

> +				     int (*match)(struct gpio_chip *gc,
> +						  void *data))

One line?
Or maybe a type for it? (gpio_match_fn, for example)

> +{
> +	struct gpio_device *gdev;
> +
> +	guard(spinlock_irqsave)(&gpio_lock);
> +
> +	list_for_each_entry(gdev, &gpio_devices, list) {
> +		if (gdev->chip && match(gdev->chip, data))
> +			return gpio_device_get(gdev);
> +	}
> +
> +	return NULL;
> +}

...

> +struct gpio_device *gpio_device_find(void *data,
> +				     int (*match)(struct gpio_chip *gc,
> +						  void *data));

Ditto.
Linus Walleij Sept. 7, 2023, 7:05 a.m. UTC | #2
On Tue, Sep 5, 2023 at 8:53 PM Bartosz Golaszewski <brgl@bgdev.pl> wrote:

> From: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
>
> gpiochip_find() is wrong and its kernel doc is misleading as the
> function doesn't return a reference to the gpio_chip but just a raw
> pointer. The chip itself is not guaranteed to stay alive, in fact it can
> be deleted at any point. Also: other than GPIO drivers themselves,
> nobody else has any business accessing gpio_chip structs.
>
> Provide a new gpio_device_find() function that returns a real reference
> to the opaque gpio_device structure that is guaranteed to stay alive for
> as long as there are active users of it.
>
> Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>


Reviewed-by: Linus Walleij <linus.walleij@linaro.org>

Yours,
Linus Walleij
Bartosz Golaszewski Sept. 11, 2023, 1:14 p.m. UTC | #3
On Wed, Sep 6, 2023 at 4:10 PM Andy Shevchenko
<andriy.shevchenko@linux.intel.com> wrote:
>
> On Tue, Sep 05, 2023 at 08:52:50PM +0200, Bartosz Golaszewski wrote:
> > From: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
> >
> > gpiochip_find() is wrong and its kernel doc is misleading as the
> > function doesn't return a reference to the gpio_chip but just a raw
> > pointer. The chip itself is not guaranteed to stay alive, in fact it can
> > be deleted at any point. Also: other than GPIO drivers themselves,
> > nobody else has any business accessing gpio_chip structs.
> >
> > Provide a new gpio_device_find() function that returns a real reference
> > to the opaque gpio_device structure that is guaranteed to stay alive for
> > as long as there are active users of it.
>
> ...
>
> > +/**
> > + * gpio_device_find() - find a specific GPIO device
> > + * @data: data to pass to match function
> > + * @match: Callback function to check gpio_chip
>
> > + * Returns:
> > + * New reference to struct gpio_device.
>
> I believe this is wrong location of the Return section.
> AFAIU how kernel doc uses section markers, this entire description becomes
> a Return(s) section. Have you tried to render man/html/pdf and see this?
>

Yes, it works just fine. Try for yourself: scripts/kernel-doc -rst
drivers/gpio/gpiolib.c

Bart

> > + * Similar to bus_find_device(). It returns a reference to a gpio_device as
> > + * determined by a user supplied @match callback. The callback should return
> > + * 0 if the device doesn't match and non-zero if it does. If the callback
> > + * returns non-zero, this function will return to the caller and not iterate
> > + * over any more gpio_devices.
> > + *
> > + * The callback takes the GPIO chip structure as argument. During the execution
> > + * of the callback function the chip is protected from being freed. TODO: This
> > + * actually has yet to be implemented.
> > + *
> > + * If the function returns non-NULL, the returned reference must be freed by
> > + * the caller using gpio_device_put().
> > + */
> > +struct gpio_device *gpio_device_find(void *data,
>
> > +                                  int (*match)(struct gpio_chip *gc,
> > +                                               void *data))
>
> One line?
> Or maybe a type for it? (gpio_match_fn, for example)
>
> > +{
> > +     struct gpio_device *gdev;
> > +
> > +     guard(spinlock_irqsave)(&gpio_lock);
> > +
> > +     list_for_each_entry(gdev, &gpio_devices, list) {
> > +             if (gdev->chip && match(gdev->chip, data))
> > +                     return gpio_device_get(gdev);
> > +     }
> > +
> > +     return NULL;
> > +}
>
> ...
>
> > +struct gpio_device *gpio_device_find(void *data,
> > +                                  int (*match)(struct gpio_chip *gc,
> > +                                               void *data));
>
> Ditto.
>
>
> --
> With Best Regards,
> Andy Shevchenko
>
>
diff mbox series

Patch

diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index f84ad54d8dbd..9e083ecb8df0 100644
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -1014,16 +1014,10 @@  void gpiochip_remove(struct gpio_chip *gc)
 }
 EXPORT_SYMBOL_GPL(gpiochip_remove);
 
-/**
- * gpiochip_find() - iterator for locating a specific gpio_chip
- * @data: data to pass to match function
- * @match: Callback function to check gpio_chip
+/*
+ * FIXME: This will be removed soon.
  *
- * Similar to bus_find_device.  It returns a reference to a gpio_chip as
- * determined by a user supplied @match callback.  The callback should return
- * 0 if the device doesn't match and non-zero if it does.  If the callback is
- * non-zero, this function will return to the caller and not iterate over any
- * more gpio_chips.
+ * This function is depracated, don't use.
  */
 struct gpio_chip *gpiochip_find(void *data,
 				int (*match)(struct gpio_chip *gc,
@@ -1031,21 +1025,55 @@  struct gpio_chip *gpiochip_find(void *data,
 {
 	struct gpio_device *gdev;
 	struct gpio_chip *gc = NULL;
-	unsigned long flags;
 
-	spin_lock_irqsave(&gpio_lock, flags);
-	list_for_each_entry(gdev, &gpio_devices, list)
-		if (gdev->chip && match(gdev->chip, data)) {
-			gc = gdev->chip;
-			break;
-		}
-
-	spin_unlock_irqrestore(&gpio_lock, flags);
+	gdev = gpio_device_find(data, match);
+	if (gdev) {
+		gc = gdev->chip;
+		gpio_device_put(gdev);
+	}
 
 	return gc;
 }
 EXPORT_SYMBOL_GPL(gpiochip_find);
 
+/**
+ * gpio_device_find() - find a specific GPIO device
+ * @data: data to pass to match function
+ * @match: Callback function to check gpio_chip
+ *
+ * Returns:
+ * New reference to struct gpio_device.
+ *
+ * Similar to bus_find_device(). It returns a reference to a gpio_device as
+ * determined by a user supplied @match callback. The callback should return
+ * 0 if the device doesn't match and non-zero if it does. If the callback
+ * returns non-zero, this function will return to the caller and not iterate
+ * over any more gpio_devices.
+ *
+ * The callback takes the GPIO chip structure as argument. During the execution
+ * of the callback function the chip is protected from being freed. TODO: This
+ * actually has yet to be implemented.
+ *
+ * If the function returns non-NULL, the returned reference must be freed by
+ * the caller using gpio_device_put().
+ */
+struct gpio_device *gpio_device_find(void *data,
+				     int (*match)(struct gpio_chip *gc,
+						  void *data))
+{
+	struct gpio_device *gdev;
+
+	guard(spinlock_irqsave)(&gpio_lock);
+
+	list_for_each_entry(gdev, &gpio_devices, list) {
+		if (gdev->chip && match(gdev->chip, data))
+			return gpio_device_get(gdev);
+	}
+
+	return NULL;
+}
+EXPORT_SYMBOL_GPL(gpio_device_find);
+
 static int gpiochip_match_name(struct gpio_chip *gc, void *data)
 {
 	const char *name = data;
diff --git a/include/linux/gpio/driver.h b/include/linux/gpio/driver.h
index a2060dc3344b..5c5029cec226 100644
--- a/include/linux/gpio/driver.h
+++ b/include/linux/gpio/driver.h
@@ -606,6 +606,10 @@  int devm_gpiochip_add_data_with_key(struct device *dev, struct gpio_chip *gc,
 struct gpio_chip *gpiochip_find(void *data,
 				int (*match)(struct gpio_chip *gc, void *data));
 
+struct gpio_device *gpio_device_find(void *data,
+				     int (*match)(struct gpio_chip *gc,
+						  void *data));
+
 struct gpio_device *gpio_device_get(struct gpio_device *gdev);
 void gpio_device_put(struct gpio_device *gdev);