* Re: [PATCH 2/7] driver core: create class_is_registered()
2023-03-31 9:33 ` [PATCH 2/7] driver core: create class_is_registered() Greg Kroah-Hartman
@ 2023-03-31 10:16 ` Rafael J. Wysocki
2023-03-31 12:44 ` Linus Walleij
1 sibling, 0 replies; 3+ messages in thread
From: Rafael J. Wysocki @ 2023-03-31 10:16 UTC (permalink / raw)
To: Greg Kroah-Hartman
Cc: linux-kernel, Linus Walleij, Bartosz Golaszewski,
Sebastian Reichel, Benjamin Tissoires, linux-gpio,
Rafael J. Wysocki
On Fri, Mar 31, 2023 at 11:33 AM Greg Kroah-Hartman
<gregkh@linuxfoundation.org> wrote:
>
> Some classes (i.e. gpio), want to know if they have been registered or
> not, and poke around in the class's internal structures to try to figure
> this out. Because this is not really a good idea, provide a function
> for classes to call to try to figure this out.
>
> Note, this is racy as the state of the class could change at any moment
> in time after the call is made, but as usually a class only wants to
> know if it has been registered yet or not, it should be fairly safe to
> use, and is just as safe as the previous "poke at the class internals"
> check was.
>
> Move the gpiolib code to use this function as proof that it works
> properly.
>
> Cc: Linus Walleij <linus.walleij@linaro.org>
> Cc: Bartosz Golaszewski <brgl@bgdev.pl>
> Cc: Sebastian Reichel <sre@kernel.org>
> Cc: Benjamin Tissoires <benjamin.tissoires@redhat.com>
> Cc: linux-gpio@vger.kernel.org
> Cc: "Rafael J. Wysocki" <rafael@kernel.org>
> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-by: Rafael J. Wysocki <rafael@kernel.org>
> ---
> drivers/base/class.c | 25 +++++++++++++++++++++++++
> drivers/gpio/gpiolib-sysfs.c | 4 ++--
> include/linux/device/class.h | 1 +
> 3 files changed, 28 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/base/class.c b/drivers/base/class.c
> index 68a6f9b56d19..a8a1bf976290 100644
> --- a/drivers/base/class.c
> +++ b/drivers/base/class.c
> @@ -634,6 +634,31 @@ void class_compat_remove_link(struct class_compat *cls, struct device *dev,
> }
> EXPORT_SYMBOL_GPL(class_compat_remove_link);
>
> +/**
> + * class_is_registered - determine if at this moment in time, a class is
> + * registered in the driver core or not.
> + * @class: the class to check
> + *
> + * Returns a boolean to state if the class is registered in the driver core
> + * or not. Note that the value could switch right after this call is made,
> + * so only use this in places where you "know" it is safe to do so (usually
> + * to determine if the specific class has been registered yet or not).
> + *
> + * Be careful in using this.
> + */
> +bool class_is_registered(const struct class *class)
> +{
> + struct subsys_private *sp = class_to_subsys(class);
> + bool is_initialized = false;
> +
> + if (sp) {
> + is_initialized = true;
> + subsys_put(sp);
> + }
> + return is_initialized;
> +}
> +EXPORT_SYMBOL_GPL(class_is_registered);
> +
> int __init classes_init(void)
> {
> class_kset = kset_create_and_add("class", NULL, NULL);
> diff --git a/drivers/gpio/gpiolib-sysfs.c b/drivers/gpio/gpiolib-sysfs.c
> index a895915affa5..1a9b21731cc9 100644
> --- a/drivers/gpio/gpiolib-sysfs.c
> +++ b/drivers/gpio/gpiolib-sysfs.c
> @@ -554,7 +554,7 @@ int gpiod_export(struct gpio_desc *desc, bool direction_may_change)
> int offset;
>
> /* can't export until sysfs is available ... */
> - if (!gpio_class.p) {
> + if (!class_is_registered(&gpio_class)) {
> pr_debug("%s: called too early!\n", __func__);
> return -ENOENT;
> }
> @@ -728,7 +728,7 @@ int gpiochip_sysfs_register(struct gpio_device *gdev)
> * register later, in gpiolib_sysfs_init() ... here we just
> * verify that _some_ field of gpio_class got initialized.
> */
> - if (!gpio_class.p)
> + if (!class_is_registered(&gpio_class))
> return 0;
>
> /*
> diff --git a/include/linux/device/class.h b/include/linux/device/class.h
> index b53728ca56fb..9cb5db0588c8 100644
> --- a/include/linux/device/class.h
> +++ b/include/linux/device/class.h
> @@ -84,6 +84,7 @@ extern struct kobject *sysfs_dev_block_kobj;
>
> int __must_check class_register(struct class *class);
> void class_unregister(const struct class *class);
> +bool class_is_registered(const struct class *class);
>
> struct class_compat;
> struct class_compat *class_compat_register(const char *name);
> --
> 2.40.0
>
^ permalink raw reply [flat|nested] 3+ messages in thread* Re: [PATCH 2/7] driver core: create class_is_registered()
2023-03-31 9:33 ` [PATCH 2/7] driver core: create class_is_registered() Greg Kroah-Hartman
2023-03-31 10:16 ` Rafael J. Wysocki
@ 2023-03-31 12:44 ` Linus Walleij
1 sibling, 0 replies; 3+ messages in thread
From: Linus Walleij @ 2023-03-31 12:44 UTC (permalink / raw)
To: Greg Kroah-Hartman
Cc: linux-kernel, Bartosz Golaszewski, Sebastian Reichel,
Benjamin Tissoires, linux-gpio, Rafael J. Wysocki
On Fri, Mar 31, 2023 at 11:33 AM Greg Kroah-Hartman
<gregkh@linuxfoundation.org> wrote:
> Some classes (i.e. gpio), want to know if they have been registered or
> not, and poke around in the class's internal structures to try to figure
> this out. Because this is not really a good idea, provide a function
> for classes to call to try to figure this out.
>
> Note, this is racy as the state of the class could change at any moment
> in time after the call is made, but as usually a class only wants to
> know if it has been registered yet or not, it should be fairly safe to
> use, and is just as safe as the previous "poke at the class internals"
> check was.
>
> Move the gpiolib code to use this function as proof that it works
> properly.
>
> Cc: Linus Walleij <linus.walleij@linaro.org>
> Cc: Bartosz Golaszewski <brgl@bgdev.pl>
> Cc: Sebastian Reichel <sre@kernel.org>
> Cc: Benjamin Tissoires <benjamin.tissoires@redhat.com>
> Cc: linux-gpio@vger.kernel.org
> Cc: "Rafael J. Wysocki" <rafael@kernel.org>
> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This looks good to me!
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Yours,
Linus Walleij
^ permalink raw reply [flat|nested] 3+ messages in thread