[PATCH v9 3/9] gpio: Add revocable provider handle for struct gpio_chip

[Tzung-Bi Shih]

The underlying chip can be removed asynchronously.  `gdev->srcu` is used
to ensure the synchronization before accessing `gdev->chip`.

Revocable encapsulates the details.  Add revocable provider handle for
the corresponding struct gpio_chip in struct gpio_device so that it can
start to hide the synchronization details.

Signed-off-by: Tzung-Bi Shih <tzungbi@xxxxxxxxxx>
---
v9:
- New to the series.
- Use static allocated resource provider.
- Rename "chip_rp" -> "chip_rev".

v4 - v8:
- Doesn't exist.

v3: https://lore.kernel.org/all/20260213092958.864411-8-tzungbi@xxxxxxxxxx
- Change revocable API usages accordingly.

v2: https://lore.kernel.org/all/20260203061059.975605-8-tzungbi@xxxxxxxxxx
- Change usages accordingly after applying
  https://lore.kernel.org/all/20260129143733.45618-2-tzungbi@xxxxxxxxxx.
  - Add __rcu for `chip_rp`.
  - Pass pointer of pointer to revocable_provider_revoke().
- Rebase accordingly after applying
  https://lore.kernel.org/all/20260203060210.972243-1-tzungbi@xxxxxxxxxx.

v1: https://lore.kernel.org/all/20260116081036.352286-13-tzungbi@xxxxxxxxxx

---
 drivers/gpio/gpiolib.c | 7 +++++++
 drivers/gpio/gpiolib.h | 3 +++
 2 files changed, 10 insertions(+)

diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index 1e6dce430dca..20448d5aab93 100644
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -23,6 +23,7 @@
 #include <linux/nospec.h>
 #include <linux/of.h>
 #include <linux/pinctrl/consumer.h>
+#include <linux/revocable.h>
 #include <linux/seq_file.h>
 #include <linux/slab.h>
 #include <linux/srcu.h>
@@ -874,6 +875,7 @@ static void gpiodev_release(struct device *dev)
 	synchronize_srcu(&gdev->desc_srcu);
 	cleanup_srcu_struct(&gdev->desc_srcu);
 
+	revocable_embed_destroy(&gdev->chip_rev);
 	ida_free(&gpio_ida, gdev->id);
 	kfree_const(gdev->label);
 	kfree(gdev->descs);
@@ -1167,6 +1169,10 @@ int gpiochip_add_data_with_key(struct gpio_chip *gc, void *data,
 	if (ret)
 		goto err_cleanup_desc_srcu;
 
+	ret = revocable_embed_init(&gdev->chip_rev, gc);
+	if (ret)
+		goto err_cleanup_desc_srcu;
+
 	device_initialize(&gdev->dev);
 	/*
 	 * After this point any allocated resources to `gdev` will be
@@ -1389,6 +1395,7 @@ void gpiochip_remove(struct gpio_chip *gc)
 	/* Numb the device, cancelling all outstanding operations */
 	rcu_assign_pointer(gdev->chip, NULL);
 	synchronize_srcu(&gdev->srcu);
+	revocable_revoke(&gdev->chip_rev);
 	gpio_device_teardown_shared(gdev);
 	gpiochip_irqchip_remove(gc);
 	acpi_gpiochip_remove(gc);
diff --git a/drivers/gpio/gpiolib.h b/drivers/gpio/gpiolib.h
index dc4cb61a9318..4e2e98f61f5a 100644
--- a/drivers/gpio/gpiolib.h
+++ b/drivers/gpio/gpiolib.h
@@ -16,6 +16,7 @@
 #include <linux/gpio/driver.h>
 #include <linux/module.h>
 #include <linux/notifier.h>
+#include <linux/revocable.h>
 #include <linux/spinlock.h>
 #include <linux/string.h>
 #include <linux/srcu.h>
@@ -55,6 +56,7 @@ struct fwnode_handle;
  * @device_notifier: used to notify character device wait queues about the GPIO
  *                   device being unregistered
  * @srcu: protects the pointer to the underlying GPIO chip
+ * @chip_rev: revocable provider handle for the corresponding struct gpio_chip.
  * @pin_ranges: range of pins served by the GPIO driver
  *
  * This state container holds most of the runtime variable data
@@ -82,6 +84,7 @@ struct gpio_device {
 	struct workqueue_struct	*line_state_wq;
 	struct blocking_notifier_head device_notifier;
 	struct srcu_struct	srcu;
+	struct revocable	chip_rev;
 
 #ifdef CONFIG_PINCTRL
 	/*
-- 
2.51.0