| Message ID | 20230927142931.19798-4-brgl@bgdev.pl |
|---|---|
| State | New |
| Headers | show |
| Series | gpiolib: work towards removing gpiochip_find() | expand |
On Wed, Sep 27, 2023 at 04:29:23PM +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. ... > struct gpio_chip *gpiochip_find(void *data, > int (*match)(struct gpio_chip *gc, > +struct gpio_device *gpio_device_find(void *data, > + int (*match)(struct gpio_chip *gc, > + void *data)) Why not typedef int (*gpio_chip_match_fn)(struct gpio_chip *gc, void *data); ?
On Mon, Oct 2, 2023 at 11:42 AM Andy Shevchenko <andriy.shevchenko@linux.intel.com> wrote: > > On Wed, Sep 27, 2023 at 04:29:23PM +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. > > ... > > > struct gpio_chip *gpiochip_find(void *data, > > int (*match)(struct gpio_chip *gc, > > > +struct gpio_device *gpio_device_find(void *data, > > + int (*match)(struct gpio_chip *gc, > > + void *data)) > > Why not > > typedef int (*gpio_chip_match_fn)(struct gpio_chip *gc, void *data); > Because gpiochip_find() will go away as soon as we convert all users. Bart > ? > > -- > With Best Regards, > Andy Shevchenko > >
On Mon, Oct 02, 2023 at 11:52:52AM +0200, Bartosz Golaszewski wrote: > On Mon, Oct 2, 2023 at 11:42 AM Andy Shevchenko > <andriy.shevchenko@linux.intel.com> wrote: > > On Wed, Sep 27, 2023 at 04:29:23PM +0200, Bartosz Golaszewski wrote: > > > From: Bartosz Golaszewski <bartosz.golaszewski@linaro.org> ... > > > struct gpio_chip *gpiochip_find(void *data, > > > int (*match)(struct gpio_chip *gc, > > > > > +struct gpio_device *gpio_device_find(void *data, > > > + int (*match)(struct gpio_chip *gc, > > > + void *data)) > > > > Why not > > > > typedef int (*gpio_chip_match_fn)(struct gpio_chip *gc, void *data); > > Because gpiochip_find() will go away as soon as we convert all users. And gpio_device_find() does not. So, I didn't get this argument.
On Mon, Oct 2, 2023 at 11:57 AM Andy Shevchenko <andriy.shevchenko@linux.intel.com> wrote: > > On Mon, Oct 02, 2023 at 11:52:52AM +0200, Bartosz Golaszewski wrote: > > On Mon, Oct 2, 2023 at 11:42 AM Andy Shevchenko > > <andriy.shevchenko@linux.intel.com> wrote: > > > On Wed, Sep 27, 2023 at 04:29:23PM +0200, Bartosz Golaszewski wrote: > > > > From: Bartosz Golaszewski <bartosz.golaszewski@linaro.org> > > ... > > > > > struct gpio_chip *gpiochip_find(void *data, > > > > int (*match)(struct gpio_chip *gc, > > > > > > > +struct gpio_device *gpio_device_find(void *data, > > > > + int (*match)(struct gpio_chip *gc, > > > > + void *data)) > > > > > > Why not > > > > > > typedef int (*gpio_chip_match_fn)(struct gpio_chip *gc, void *data); > > > > Because gpiochip_find() will go away as soon as we convert all users. > > And gpio_device_find() does not. So, I didn't get this argument. > This symbol would only be used in a single place. But whatever, I can do it as there will be another respin anyway. Bart
diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c index f84ad54d8dbd..0371d23f0a46 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 +1025,62 @@ 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; + + /* + * Not yet but in the future the spinlock below will become a mutex. + * Annotate this function before anyone tries to use it in interrupt + * context like it happened with gpiochip_find(). + */ + might_sleep(); + + 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 1cedbc3d3200..6ad1f1a8ef2e 100644 --- a/include/linux/gpio/driver.h +++ b/include/linux/gpio/driver.h @@ -608,6 +608,9 @@ 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);