Merge tag 'trace-v7.3-2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-tracegrafted

Pull tracing fixes from Steven Rostedt:

 - Fix error output of boot instance creation failure

   Currently if a boot instance creation fails, instead of printing out
   the name of the instance that failed, it prints "(null)". That is
   because it prints "cur_str" that had already been processed by
   strsep(). Print the saved name instead.

   While at it, print the error code of the failure.

 - Fix use-after-free for same named historgrams

   Histograms can be named so that they can be used in multiple events.
   But if the named histogram has a variable attached, the second event
   that uses the named histogram which duplicates it and needs to free
   the original after duplication leaves the old variable in place and
   still visible. If another histogram uses than variable, it will use
   the stale one which will try to reference the freed duplicate
   histogram and crash the kernel.

   Free the duplicate variables along with the duplicated histogram
   data.

 - Check return value of kthread_run() in event self test

   The events self tests uses a kthread for testing but does not check
   if it succeeded in creating a kthread. If the kthread creation were
   to fail, the code will still try to call kthread_stop() on the error
   returned.

 - Fix race between reading trace_pipe and updating subbuffer size

   If a user is reading the trace_pipe file at the same time they update
   the ring buffer sub-buffer size, can cause the trace_pipe read to
   read stale data. Add trace_access_lock() around updating the ring
   buffer sub-buffer size.

 - Fix eventfs_inode on failure path in creation of the events directory

   In the creation of the "events" directory, if after allocating the
   eventfs_inode a failure is detected, it calls cleanup_ei() which
   calls free_ei(). The free_ei() will test if eventfs_inode being freed
   has no children. It is a bug if it does. But on the failure case of
   the creation of the "events" directory, the children lists have not
   yet been initialized and the free will trigger a warning because
   list_empty() on an uninitialized list returns false.

   Move the initialization into init_ei() where it makes more sense and
   makes sure that a created eventfs_inode has its lists initialized
   upon creation.

 - Check return value of kthread_run() in ftrace direct sample code

   The sample code that shows how to use the ftrace direct calls does
   not test the return of kthread_run() to see if it succeeds. Return a
   failure if the kthread_run() doesn't succeed.

 - Clear user events state on fork in case of alloc failure

   On fork, the child gets a pointer to the parent's user events state.
   It makes a copy of it then updates the child's pointer to it. But if
   the allocation fails, the duplication function leaves the child with
   a pointer to its parent's descriptor. When the child cleans up its
   data, it will free the parent's descriptor while the parent is still
   using it.

   In the duplication function, set the child's user_event_mm to NULL
   before testing if the allocation succeeded, and when it exits it will
   not free the parent's descriptor.

 - Fix retry exhaustion in simple ring buffer reader swap

   simple_ring_buffer_swap_reader_page() starts with retry set to 8 and
   post-decrements it only after a failed link replacement. On the final
   attempt, a successful replacement leaves retry at zero, while a
   failed replacement leaves it at -1.

   But the check for success expects the retry value to be non-zero and
   exits with an error on zero. This is the opposite result. Fix it.

 - Fail nicely when the remote swap_reader_page() returns an error

   Currently, if the swap_reader_page() of a remote buffer fails, it
   triggers a WARN_ON_ONCE() and continues normally. Instead, have it
   exit with an error and a pr_warn() print instead of a full WARNING.

* tag 'trace-v7.3-2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace:
  ring-buffer: Stop remote reader update when page swap fails
  tracing: Fix retry exhaustion in simple ring buffer reader swap
  tracing/user_events: Clear copied tracing state before fork duplication
  samples/ftrace: Fix kthread_stop() on ERR_PTR in ftrace-direct-multi-modify
  samples/ftrace: Fix kthread_stop() on ERR_PTR in ftrace-direct-modify
  eventfs: Initialize ei->children and ei->list in init_ei()
  tracing: Fix use-after-free in trace_pipe read on sub-buffer order change
  tracing: Fix crash passing ERR_PTR to kthread_stop()
  tracing: Fix use-after-free with same-name named triggers
  tracing: Fix logged instance name on creation failure

1 files changed, 797 insertions, 0 deletions

diff --git a/drivers/gpio/gpiolib-shared.c b/drivers/gpio/gpiolib-shared.c
new file mode 100644
index 000000000..495bd3d0d
--- /dev/null
+++ b/drivers/gpio/gpiolib-shared.c
@@ -0,0 +1,797 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2025 Linaro Ltd.
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/auxiliary_bus.h>
+#include <linux/cleanup.h>
+#include <linux/device.h>
+#include <linux/fwnode.h>
+#include <linux/gpio/consumer.h>
+#include <linux/gpio/machine.h>
+#include <linux/idr.h>
+#include <linux/kref.h>
+#include <linux/list.h>
+#include <linux/lockdep.h>
+#include <linux/module.h>
+#include <linux/mutex.h>
+#include <linux/of.h>
+#include <linux/overflow.h>
+#include <linux/printk.h>
+#include <linux/property.h>
+#include <linux/slab.h>
+#include <linux/string.h>
+
+#include "gpiolib.h"
+#include "gpiolib-shared.h"
+
+/* Represents a single reference to a GPIO pin. */
+struct gpio_shared_ref {
+	struct list_head list;
+	/* Firmware node associated with this GPIO's consumer. */
+	struct fwnode_handle *fwnode;
+	/* GPIO flags this consumer uses for the request. */
+	enum gpiod_flags flags;
+	char *con_id;
+	int dev_id;
+	/* Protects the auxiliary device struct and the lookup table. */
+	struct mutex lock;
+	struct lock_class_key lock_key;
+	struct auxiliary_device adev;
+	struct gpiod_lookup_table *lookup;
+	bool is_reset_gpio;
+};
+
+/* Represents a single GPIO pin. */
+struct gpio_shared_entry {
+	struct list_head list;
+	/* Firmware node associated with the GPIO controller. */
+	struct fwnode_handle *fwnode;
+	/* Hardware offset of the GPIO within its chip. */
+	unsigned int offset;
+	/* Index in the property value array. */
+	size_t index;
+	/* Synchronizes the modification of shared_desc and offset. */
+	struct mutex lock;
+	struct gpio_shared_desc *shared_desc;
+	struct kref ref;
+	struct list_head refs;
+};
+
+static LIST_HEAD(gpio_shared_list);
+static DEFINE_IDA(gpio_shared_ida);
+
+#if IS_ENABLED(CONFIG_OF)
+static struct gpio_shared_entry *
+gpio_shared_find_entry(struct fwnode_handle *controller_node,
+		       unsigned int offset)
+{
+	struct gpio_shared_entry *entry;
+
+	list_for_each_entry(entry, &gpio_shared_list, list) {
+		if (entry->fwnode == controller_node && entry->offset == offset)
+			return entry;
+	}
+
+	return NULL;
+}
+
+static struct gpio_shared_ref *gpio_shared_make_ref(struct fwnode_handle *fwnode,
+						    const char *con_id,
+						    enum gpiod_flags flags)
+{
+	char *con_id_cpy __free(kfree) = NULL;
+
+	struct gpio_shared_ref *ref __free(kfree) = kzalloc_obj(*ref);
+	if (!ref)
+		return NULL;
+
+	if (con_id) {
+		con_id_cpy = kstrdup(con_id, GFP_KERNEL);
+		if (!con_id_cpy)
+			return NULL;
+	}
+
+	ref->dev_id = ida_alloc(&gpio_shared_ida, GFP_KERNEL);
+	if (ref->dev_id < 0)
+		return NULL;
+
+	ref->flags = flags;
+	ref->con_id = no_free_ptr(con_id_cpy);
+	ref->fwnode = fwnode;
+	lockdep_register_key(&ref->lock_key);
+	mutex_init_with_key(&ref->lock, &ref->lock_key);
+
+	return no_free_ptr(ref);
+}
+
+static int gpio_shared_setup_reset_proxy(struct gpio_shared_entry *entry,
+					 enum gpiod_flags flags)
+{
+	struct gpio_shared_ref *ref;
+
+	list_for_each_entry(ref, &entry->refs, list) {
+		if (ref->is_reset_gpio)
+			/* Already set-up. */
+			return 0;
+	}
+
+	ref = gpio_shared_make_ref(NULL, "reset", flags);
+	if (!ref)
+		return -ENOMEM;
+
+	ref->is_reset_gpio = true;
+
+	list_add_tail(&ref->list, &entry->refs);
+
+	pr_debug("Created a secondary shared GPIO reference for potential reset-gpio device for GPIO %u at %s\n",
+		 entry->offset, fwnode_get_name(entry->fwnode));
+
+	return 0;
+}
+
+/* Handle all special nodes that we should ignore. */
+static bool gpio_shared_of_node_ignore(struct device_node *node)
+{
+	/* Ignore disabled devices. */
+	if (!of_device_is_available(node))
+		return true;
+
+	/*
+	 * __symbols__ is a special, internal node and should not be considered
+	 * when scanning for shared GPIOs.
+	 */
+	if (of_node_name_eq(node, "__symbols__"))
+		return true;
+
+	/*
+	 * GPIO hogs have a "gpios" property which is not a phandle and can't
+	 * possibly refer to a shared GPIO.
+	 */
+	if (of_property_present(node, "gpio-hog"))
+		return true;
+
+	return false;
+}
+
+static int gpio_shared_of_traverse(struct device_node *curr)
+{
+	struct gpio_shared_entry *entry;
+	size_t con_id_len, suffix_len;
+	struct fwnode_handle *fwnode;
+	struct of_phandle_args args;
+	struct gpio_shared_ref *ref;
+	struct property *prop;
+	unsigned int offset;
+	const char *suffix;
+	int ret, count, i;
+
+	if (gpio_shared_of_node_ignore(curr))
+		return 0;
+
+	for_each_property_of_node(curr, prop) {
+		/*
+		 * The standard name for a GPIO property is "foo-gpios"
+		 * or "foo-gpio". Some bindings also use "gpios" or "gpio".
+		 * There are some legacy device-trees which have a different
+		 * naming convention and for which we have rename quirks in
+		 * place in gpiolib-of.c. I don't think any of them require
+		 * support for shared GPIOs so for now let's just ignore
+		 * them. We can always just export the quirk list and
+		 * iterate over it here.
+		 */
+		if (!strends(prop->name, "-gpios") &&
+		    !strends(prop->name, "-gpio") &&
+		    strcmp(prop->name, "gpios") != 0 &&
+		    strcmp(prop->name, "gpio") != 0)
+			continue;
+
+		count = of_count_phandle_with_args(curr, prop->name,
+						   "#gpio-cells");
+		if (count <= 0)
+			continue;
+
+		for (i = 0; i < count; i++) {
+			struct device_node *np __free(device_node) = NULL;
+			char *con_id __free(kfree) = NULL;
+
+			ret = of_parse_phandle_with_args(curr, prop->name,
+							 "#gpio-cells", i,
+							 &args);
+			if (ret)
+				continue;
+
+			np = args.np;
+
+			if (!of_property_present(np, "gpio-controller"))
+				continue;
+
+			/*
+			 * We support 1, 2 and 3 cell GPIO bindings in the
+			 * kernel currently. There's only one old MIPS dts that
+			 * has a one-cell binding but there's no associated
+			 * consumer so it may as well be an error. There don't
+			 * seem to be any 3-cell users of non-exclusive GPIOs,
+			 * so we can skip this as well. Let's occupy ourselves
+			 * with the predominant 2-cell binding with the first
+			 * cell indicating the hardware offset of the GPIO and
+			 * the second defining the GPIO flags of the request.
+			 */
+			if (args.args_count != 2)
+				continue;
+
+			fwnode = of_fwnode_handle(args.np);
+			offset = args.args[0];
+
+			entry = gpio_shared_find_entry(fwnode, offset);
+			if (!entry) {
+				entry = kzalloc_obj(*entry);
+				if (!entry)
+					return -ENOMEM;
+
+				entry->fwnode = fwnode_handle_get(fwnode);
+				entry->offset = offset;
+				entry->index = count;
+				INIT_LIST_HEAD(&entry->refs);
+				mutex_init(&entry->lock);
+
+				list_add_tail(&entry->list, &gpio_shared_list);
+			}
+
+			if (strends(prop->name, "gpios"))
+				suffix = "-gpios";
+			else if (strends(prop->name, "gpio"))
+				suffix = "-gpio";
+			else
+				suffix = NULL;
+			if (!suffix)
+				continue;
+
+			/* We only set con_id if there's actually one. */
+			if (strcmp(prop->name, "gpios") && strcmp(prop->name, "gpio")) {
+				con_id = kstrdup(prop->name, GFP_KERNEL);
+				if (!con_id)
+					return -ENOMEM;
+
+				con_id_len = strlen(con_id);
+				suffix_len = strlen(suffix);
+
+				con_id[con_id_len - suffix_len] = '\0';
+			}
+
+			ref = gpio_shared_make_ref(fwnode_handle_get(of_fwnode_handle(curr)),
+						   con_id, args.args[1]);
+			if (!ref)
+				return -ENOMEM;
+
+			if (!list_empty(&entry->refs))
+				pr_debug("GPIO %u at %s is shared by multiple firmware nodes\n",
+					 entry->offset, fwnode_get_name(entry->fwnode));
+
+			list_add_tail(&ref->list, &entry->refs);
+
+			if (strcmp(prop->name, "reset-gpios") == 0) {
+				ret = gpio_shared_setup_reset_proxy(entry, args.args[1]);
+				if (ret)
+					return ret;
+			}
+		}
+	}
+
+	for_each_child_of_node_scoped(curr, child) {
+		ret = gpio_shared_of_traverse(child);
+		if (ret)
+			return ret;
+	}
+
+	return 0;
+}
+
+static int gpio_shared_of_scan(void)
+{
+	if (of_root)
+		return gpio_shared_of_traverse(of_root);
+
+	return 0;
+}
+#else
+static int gpio_shared_of_scan(void)
+{
+	return 0;
+}
+#endif /* CONFIG_OF */
+
+static void gpio_shared_adev_release(struct device *dev)
+{
+
+}
+
+static int gpio_shared_make_adev(struct gpio_device *gdev,
+				 struct gpio_shared_entry *entry,
+				 struct gpio_shared_ref *ref)
+{
+	struct auxiliary_device *adev = &ref->adev;
+	int ret;
+
+	guard(mutex)(&ref->lock);
+
+	memset(adev, 0, sizeof(*adev));
+
+	adev->id = ref->dev_id;
+	adev->name = "proxy";
+	adev->dev.parent = gdev->dev.parent;
+	adev->dev.platform_data = entry;
+	adev->dev.release = gpio_shared_adev_release;
+
+	ret = auxiliary_device_init(adev);
+	if (ret)
+		return ret;
+
+	ret = auxiliary_device_add(adev);
+	if (ret) {
+		auxiliary_device_uninit(adev);
+		return ret;
+	}
+
+	pr_debug("Created an auxiliary GPIO proxy %s for GPIO device %s\n",
+		 dev_name(&adev->dev), gpio_device_get_label(gdev));
+
+	return 0;
+}
+
+#if IS_ENABLED(CONFIG_RESET_GPIO)
+/*
+ * Special case: reset-gpio is an auxiliary device that's created dynamically
+ * and put in between the GPIO controller and consumers of shared GPIOs
+ * referred to by the "reset-gpios" property.
+ *
+ * If the supposed consumer of a shared GPIO didn't match any of the mappings
+ * we created when scanning the firmware nodes, it's still possible that it's
+ * the reset-gpio device which didn't exist at the time of the scan.
+ *
+ * This function verifies it an return true if it's the case.
+ */
+static bool gpio_shared_dev_is_reset_gpio(struct device *consumer,
+					  struct gpio_shared_entry *entry,
+					  struct gpio_shared_ref *ref)
+{
+	struct fwnode_handle *reset_fwnode = dev_fwnode(consumer);
+	struct fwnode_reference_args ref_args, aux_args;
+	struct device *parent = consumer->parent;
+	struct gpio_shared_ref *real_ref;
+	bool match;
+	int ret;
+
+	lockdep_assert_held(&ref->lock);
+
+	/* The reset-gpio device must have a parent AND a firmware node. */
+	if (!parent || !reset_fwnode)
+		return false;
+
+	/*
+	 * Parent of the reset-gpio auxiliary device is the GPIO chip whose
+	 * fwnode we stored in the entry structure.
+	 */
+	if (!device_match_fwnode(parent, entry->fwnode))
+		return false;
+
+	/*
+	 * Now we need to find the actual pin we want to assign to this
+	 * reset-gpio device. To that end: iterate over the list of references
+	 * of this entry and see if there's one, whose reset-gpios property's
+	 * arguments match the ones from this consumer's node.
+	 */
+	list_for_each_entry(real_ref, &entry->refs, list) {
+		if (real_ref == ref)
+			continue;
+
+		guard(mutex)(&real_ref->lock);
+
+		if (!real_ref->fwnode)
+			continue;
+
+		/*
+		 * The device associated with the shared reference's firmware
+		 * node is the consumer of the reset control exposed by the
+		 * reset-gpio device. It must have a "reset-gpios" property
+		 * that's referencing the entry's firmware node.
+		 *
+		 * The reference args must agree between the real consumer and
+		 * the auxiliary reset-gpio device.
+		 */
+		ret = fwnode_property_get_reference_args(real_ref->fwnode,
+							 "reset-gpios",
+							 NULL, 2, 0, &ref_args);
+		if (ret)
+			continue;
+
+		ret = fwnode_property_get_reference_args(reset_fwnode, "reset-gpios",
+							 NULL, 2, 0, &aux_args);
+		if (ret) {
+			fwnode_handle_put(ref_args.fwnode);
+			continue;
+		}
+
+		match = ((ref_args.fwnode == entry->fwnode) &&
+			 (aux_args.fwnode == entry->fwnode) &&
+			 (ref_args.args[0] == aux_args.args[0]));
+
+		fwnode_handle_put(ref_args.fwnode);
+		fwnode_handle_put(aux_args.fwnode);
+
+		if (!match)
+			continue;
+
+		/*
+		 * Reuse the fwnode of the real device, next time we'll use it
+		 * in the normal path.
+		 */
+		ref->fwnode = fwnode_handle_get(reset_fwnode);
+		return true;
+	}
+
+	return false;
+}
+#else
+static bool gpio_shared_dev_is_reset_gpio(struct device *consumer,
+					  struct gpio_shared_entry *entry,
+					  struct gpio_shared_ref *ref)
+{
+	return false;
+}
+#endif /* CONFIG_RESET_GPIO */
+
+int gpio_shared_add_proxy_lookup(struct device *consumer, struct fwnode_handle *fwnode,
+				 const char *con_id, unsigned long lflags)
+{
+	const char *dev_id = dev_name(consumer);
+	struct gpiod_lookup_table *lookup;
+	struct gpio_shared_entry *entry;
+	struct gpio_shared_ref *ref;
+
+	list_for_each_entry(entry, &gpio_shared_list, list) {
+		list_for_each_entry(ref, &entry->refs, list) {
+			guard(mutex)(&ref->lock);
+
+			if (!ref->fwnode && device_is_compatible(consumer, "reset-gpio")) {
+				if (!gpio_shared_dev_is_reset_gpio(consumer, entry, ref))
+					continue;
+			} else if (fwnode != ref->fwnode) {
+				continue;
+			}
+
+			if ((!con_id && ref->con_id) || (con_id && !ref->con_id) ||
+			    (con_id && ref->con_id && strcmp(con_id, ref->con_id) != 0))
+				continue;
+
+			/* We've already done that on a previous request. */
+			if (ref->lookup)
+				return 0;
+
+			char *key __free(kfree) =
+				kasprintf(GFP_KERNEL,
+					  KBUILD_MODNAME ".proxy.%u",
+					  ref->adev.id);
+			if (!key)
+				return -ENOMEM;
+
+			lookup = kzalloc_flex(*lookup, table, 2);
+			if (!lookup)
+				return -ENOMEM;
+
+			pr_debug("Adding machine lookup entry for a shared GPIO for consumer %s, with key '%s' and con_id '%s'\n",
+				 dev_id, key, ref->con_id ?: "none");
+
+			lookup->dev_id = dev_id;
+			lookup->table[0] = GPIO_LOOKUP(no_free_ptr(key), 0,
+						       ref->con_id, lflags);
+
+			ref->lookup = lookup;
+			gpiod_add_lookup_table(ref->lookup);
+
+			return 0;
+		}
+	}
+
+	/* We warn here because this can only happen if the programmer borked. */
+	WARN_ON(1);
+	return -ENOENT;
+}
+
+static void gpio_shared_remove_adev(struct auxiliary_device *adev)
+{
+	auxiliary_device_delete(adev);
+	auxiliary_device_uninit(adev);
+}
+
+int gpiochip_setup_shared(struct gpio_chip *gc)
+{
+	struct gpio_device *gdev = gc->gpiodev;
+	struct gpio_shared_entry *entry;
+	struct gpio_shared_ref *ref;
+	struct gpio_desc *desc;
+	int ret;
+
+	list_for_each_entry(entry, &gpio_shared_list, list) {
+		list_for_each_entry(ref, &entry->refs, list) {
+			if (gdev->dev.parent == &ref->adev.dev) {
+				/*
+				 * This is a shared GPIO proxy. Mark its
+				 * descriptor as such and return here.
+				 */
+				__set_bit(GPIOD_FLAG_SHARED_PROXY,
+					  &gdev->descs[0].flags);
+				return 0;
+			}
+		}
+	}
+
+	/*
+	 * This is not a shared GPIO proxy but it still may be the device
+	 * exposing shared pins. Find them and create the proxy devices.
+	 */
+	list_for_each_entry(entry, &gpio_shared_list, list) {
+		if (!device_match_fwnode(&gdev->dev, entry->fwnode))
+			continue;
+
+		if (list_count_nodes(&entry->refs) <= 1)
+			continue;
+
+		scoped_guard(mutex, &entry->lock) {
+#if IS_ENABLED(CONFIG_OF)
+			if (is_of_node(entry->fwnode) && gc->of_xlate) {
+				/*
+				 * This is the earliest that we can tranlate the
+				 * devicetree offset to the chip offset.
+				 */
+				struct of_phandle_args gpiospec = { };
+
+				gpiospec.np = to_of_node(entry->fwnode);
+				gpiospec.args_count = 2;
+				gpiospec.args[0] = entry->offset;
+
+				ret = gc->of_xlate(gc, &gpiospec, NULL);
+				if (ret < 0)
+					return ret;
+
+				entry->offset = ret;
+			}
+#endif /* CONFIG_OF */
+
+			desc = &gdev->descs[entry->offset];
+
+			__set_bit(GPIOD_FLAG_SHARED, &desc->flags);
+			/*
+			 * Shared GPIOs are not requested via the normal path. Make
+			 * them inaccessible to anyone even before we register the
+			 * chip.
+			 */
+			ret = gpiod_request_commit(desc, "shared");
+			if (ret)
+				return ret;
+
+			pr_debug("GPIO %u owned by %s is shared by multiple consumers\n",
+				 entry->offset, gpio_device_get_label(gdev));
+		}
+
+		list_for_each_entry(ref, &entry->refs, list) {
+			pr_debug("Setting up a shared GPIO entry for %s (con_id: '%s')\n",
+				 fwnode_get_name(ref->fwnode) ?: "(no fwnode)",
+				 ref->con_id ?: "(none)");
+
+			ret = gpio_shared_make_adev(gdev, entry, ref);
+			if (ret) {
+				gpiod_free_commit(desc);
+				return ret;
+			}
+		}
+	}
+
+	return 0;
+}
+
+void gpio_device_teardown_shared(struct gpio_device *gdev)
+{
+	struct gpio_shared_entry *entry;
+	struct gpio_shared_ref *ref;
+
+	list_for_each_entry(entry, &gpio_shared_list, list) {
+		if (!device_match_fwnode(&gdev->dev, entry->fwnode))
+			continue;
+
+		scoped_guard(mutex, &entry->lock)
+			gpiod_free_commit(&gdev->descs[entry->offset]);
+
+		list_for_each_entry(ref, &entry->refs, list) {
+			if (ref->lookup) {
+				gpiod_remove_lookup_table(ref->lookup);
+				kfree(ref->lookup->table[0].key);
+				kfree(ref->lookup);
+				ref->lookup = NULL;
+			}
+
+			gpio_shared_remove_adev(&ref->adev);
+		}
+	}
+}
+
+static void gpio_shared_release(struct kref *kref)
+{
+	struct gpio_shared_entry *entry =
+		container_of(kref, struct gpio_shared_entry, ref);
+	struct gpio_shared_desc *shared_desc;
+
+	guard(mutex)(&entry->lock);
+
+	shared_desc = entry->shared_desc;
+	gpio_device_put(shared_desc->desc->gdev);
+	mutex_destroy(&shared_desc->mutex);
+	kfree(shared_desc);
+	entry->shared_desc = NULL;
+}
+
+static void gpiod_shared_put(void *data)
+{
+	struct gpio_shared_entry *entry = data;
+
+	kref_put(&entry->ref, gpio_shared_release);
+}
+
+static struct gpio_shared_desc *
+gpiod_shared_desc_create(struct gpio_shared_entry *entry)
+{
+	struct gpio_shared_desc *shared_desc;
+	struct gpio_device *gdev;
+
+	lockdep_assert_held(&entry->lock);
+
+	shared_desc = kzalloc_obj(*shared_desc);
+	if (!shared_desc)
+		return ERR_PTR(-ENOMEM);
+
+	gdev = gpio_device_find_by_fwnode(entry->fwnode);
+	if (!gdev) {
+		kfree(shared_desc);
+		return ERR_PTR(-EPROBE_DEFER);
+	}
+
+	shared_desc->desc = &gdev->descs[entry->offset];
+	mutex_init(&shared_desc->mutex);
+
+	return shared_desc;
+}
+
+struct gpio_shared_desc *devm_gpiod_shared_get(struct device *dev)
+{
+	struct gpio_shared_desc *shared_desc;
+	struct gpio_shared_entry *entry;
+	int ret;
+
+	entry = dev_get_platdata(dev);
+	if (WARN_ON(!entry))
+		/* Programmer bug */
+		return ERR_PTR(-ENOENT);
+
+	scoped_guard(mutex, &entry->lock) {
+		if (entry->shared_desc) {
+			kref_get(&entry->ref);
+			shared_desc = entry->shared_desc;
+		} else {
+			shared_desc = gpiod_shared_desc_create(entry);
+			if (IS_ERR(shared_desc))
+				return ERR_CAST(shared_desc);
+
+			kref_init(&entry->ref);
+			entry->shared_desc = shared_desc;
+		}
+
+		pr_debug("Device %s acquired a reference to the shared GPIO %u owned by %s\n",
+			 dev_name(dev), gpiod_hwgpio(shared_desc->desc),
+			 gpio_device_get_label(shared_desc->desc->gdev));
+	}
+
+	ret = devm_add_action_or_reset(dev, gpiod_shared_put, entry);
+	if (ret)
+		return ERR_PTR(ret);
+
+	return shared_desc;
+}
+EXPORT_SYMBOL_GPL(devm_gpiod_shared_get);
+
+static void gpio_shared_drop_ref(struct gpio_shared_ref *ref)
+{
+	list_del(&ref->list);
+	mutex_destroy(&ref->lock);
+	lockdep_unregister_key(&ref->lock_key);
+	kfree(ref->con_id);
+	ida_free(&gpio_shared_ida, ref->dev_id);
+	fwnode_handle_put(ref->fwnode);
+	kfree(ref);
+}
+
+static void gpio_shared_drop_entry(struct gpio_shared_entry *entry)
+{
+	list_del(&entry->list);
+	mutex_destroy(&entry->lock);
+	fwnode_handle_put(entry->fwnode);
+	kfree(entry);
+}
+
+/*
+ * This is only called if gpio_shared_init() fails so it's in fact __init and
+ * not __exit.
+ */
+static void __init gpio_shared_teardown(void)
+{
+	struct gpio_shared_entry *entry, *epos;
+	struct gpio_shared_ref *ref, *rpos;
+
+	list_for_each_entry_safe(entry, epos, &gpio_shared_list, list) {
+		list_for_each_entry_safe(ref, rpos, &entry->refs, list)
+			gpio_shared_drop_ref(ref);
+
+		gpio_shared_drop_entry(entry);
+	}
+}
+
+static bool gpio_shared_entry_is_really_shared(struct gpio_shared_entry *entry)
+{
+	size_t num_nodes = list_count_nodes(&entry->refs);
+	struct gpio_shared_ref *ref;
+
+	if (num_nodes <= 1)
+		return false;
+
+	if (num_nodes > 2)
+		return true;
+
+	/* Exactly two references: */
+	list_for_each_entry(ref, &entry->refs, list) {
+		/*
+		 * Corner-case: the second reference comes from the potential
+		 * reset-gpio instance. However, this pin is not really shared
+		 * as it would have three references in this case. Avoid
+		 * creating unnecessary proxies.
+		 */
+		if (ref->is_reset_gpio)
+			return false;
+	}
+
+	return true;
+}
+
+static void gpio_shared_free_exclusive(void)
+{
+	struct gpio_shared_entry *entry, *epos;
+	struct gpio_shared_ref *ref, *rpos;
+
+	list_for_each_entry_safe(entry, epos, &gpio_shared_list, list) {
+		if (gpio_shared_entry_is_really_shared(entry))
+			continue;
+
+		list_for_each_entry_safe(ref, rpos, &entry->refs, list)
+			gpio_shared_drop_ref(ref);
+		gpio_shared_drop_entry(entry);
+	}
+}
+
+static int __init gpio_shared_init(void)
+{
+	int ret;
+
+	/* Right now, we only support OF-based systems. */
+	ret = gpio_shared_of_scan();
+	if (ret) {
+		gpio_shared_teardown();
+		pr_err("Failed to scan OF nodes for shared GPIOs: %d\n", ret);
+		return ret;
+	}
+
+	gpio_shared_free_exclusive();
+
+	pr_debug("Finished scanning firmware nodes for shared GPIOs\n");
+	return 0;
+}
+postcore_initcall(gpio_shared_init);