gpio: cdev: bail out of poll() if the device goes down

index 0a33971c964c..062521e1a9e0 100644
@@ -2502,22 +2502,33 @@ static int lineinfo_changed_notify(struct notifier_block *nb,
 {
 	struct gpio_chardev_data *cdev = to_gpio_chardev_data(nb);
 	struct gpio_v2_line_info_changed chg;
-	struct gpio_desc *desc = data;
+	struct gpio_desc *desc;
 	int ret;
 
-	if (!test_bit(gpio_chip_hwgpio(desc), cdev->watched_lines))
-		return NOTIFY_DONE;
+	switch (action) {
+	case GPIO_V2_LINE_CHANGED_REQUESTED:
+	case GPIO_V2_LINE_CHANGED_RELEASED:
+	case GPIO_V2_LINE_CHANGED_CONFIG:
+		desc = data;
 
-	memset(&chg, 0, sizeof(chg));
-	chg.event_type = action;
-	chg.timestamp_ns = ktime_get_ns();
-	gpio_desc_to_lineinfo(desc, &chg.info);
+		if (!test_bit(gpio_chip_hwgpio(desc), cdev->watched_lines))
+			return NOTIFY_DONE;
 
-	ret = kfifo_in_spinlocked(&cdev->events, &chg, 1, &cdev->wait.lock);
-	if (ret)
-		wake_up_poll(&cdev->wait, EPOLLIN);
-	else
-		pr_debug_ratelimited("lineinfo event FIFO is full - event dropped\n");
+		memset(&chg, 0, sizeof(chg));
+		chg.event_type = action;
+		chg.timestamp_ns = ktime_get_ns();
+		gpio_desc_to_lineinfo(desc, &chg.info);
+
+		ret = kfifo_in_spinlocked(&cdev->events, &chg, 1,
+					  &cdev->wait.lock);
+		if (ret)
+			wake_up_poll(&cdev->wait, EPOLLIN);
+		else
+			pr_debug_ratelimited("lineinfo event FIFO is full - event dropped\n");
+		break;
+	default:
+		return NOTIFY_DONE;
+	}
 
 	return NOTIFY_OK;
 }

index cca81375f127..de7b3b60f7ca 100644
@@ -38,8 +38,7 @@
  * or name of the IP component in a System on Chip.
  * @data: per-instance data assigned by the driver
  * @list: links gpio_device:s together for traversal
- * @notifier: used to notify subscribers about lines being requested, released
- *            or reconfigured
+ * @notifier: used to notify subscribers about gpio_device events
  * @sem: protects the structure from a NULL-pointer dereference of @chip by
  *       user-space operations when the device gets unregistered during
  *       a hot-unplug event

index 062521e1a9e0..660d2e057451 100644
@@ -2319,7 +2319,7 @@ struct gpio_chardev_data {
 	struct gpio_device *gdev;
 	wait_queue_head_t wait;
 	DECLARE_KFIFO(events, struct gpio_v2_line_info_changed, 32);
-	struct notifier_block lineinfo_changed_nb;
+	struct notifier_block nb;
 	unsigned long *watched_lines;
 #ifdef CONFIG_GPIO_CDEV_V1
 	atomic_t watch_abi_version;

@@ -2494,11 +2494,11 @@ static long gpio_ioctl_compat(struct file *file, unsigned int cmd,
 static struct gpio_chardev_data *
 to_gpio_chardev_data(struct notifier_block *nb)
 {
-	return container_of(nb, struct gpio_chardev_data, lineinfo_changed_nb);
+	return container_of(nb, struct gpio_chardev_data, nb);
 }
 
-static int lineinfo_changed_notify(struct notifier_block *nb,
-				   unsigned long action, void *data)
+static int gpio_chardev_notify(struct notifier_block *nb, unsigned long action,
+			       void *data)
 {
 	struct gpio_chardev_data *cdev = to_gpio_chardev_data(nb);
 	struct gpio_v2_line_info_changed chg;

@@ -2681,9 +2681,8 @@ static int gpio_chrdev_open(struct inode *inode, struct file *file)
 	INIT_KFIFO(cdev->events);
 	cdev->gdev = gpio_device_get(gdev);
 
-	cdev->lineinfo_changed_nb.notifier_call = lineinfo_changed_notify;
-	ret = blocking_notifier_chain_register(&gdev->notifier,
-					       &cdev->lineinfo_changed_nb);
+	cdev->nb.notifier_call = gpio_chardev_notify;
+	ret = blocking_notifier_chain_register(&gdev->notifier, &cdev->nb);
 	if (ret)
 		goto out_free_bitmap;
 

@@ -2698,8 +2697,7 @@ static int gpio_chrdev_open(struct inode *inode, struct file *file)
 	return ret;
 
 out_unregister_notifier:
-	blocking_notifier_chain_unregister(&gdev->notifier,
-					   &cdev->lineinfo_changed_nb);
+	blocking_notifier_chain_unregister(&gdev->notifier, &cdev->nb);
 out_free_bitmap:
 	gpio_device_put(gdev);
 	bitmap_free(cdev->watched_lines);

@@ -2722,8 +2720,7 @@ static int gpio_chrdev_release(struct inode *inode, struct file *file)
 	struct gpio_device *gdev = cdev->gdev;
 
 	bitmap_free(cdev->watched_lines);
-	blocking_notifier_chain_unregister(&gdev->notifier,
-					   &cdev->lineinfo_changed_nb);
+	blocking_notifier_chain_unregister(&gdev->notifier, &cdev->nb);
 	gpio_device_put(gdev);
 	kfree(cdev);
 

index 660d2e057451..eb8c0cb71da4 100644
@@ -32,6 +32,12 @@
 #include "gpiolib.h"
 #include "gpiolib-cdev.h"
 
+/*
+ * Let's use a higher value for gpio_device notifications to not conflict with
+ * UAPI defines that can also serve as notifier action arguments.
+ */
+#define GPIO_CDEV_UNREGISTERED	1000
+
 /*
  * Array sizes must ensure 64-bit alignment and not create holes in the
  * struct packing.

@@ -2526,6 +2532,9 @@ static int gpio_chardev_notify(struct notifier_block *nb, unsigned long action,
 		else
 			pr_debug_ratelimited("lineinfo event FIFO is full - event dropped\n");
 		break;
+	case GPIO_CDEV_UNREGISTERED:
+		wake_up_poll(&cdev->wait, EPOLLIN | EPOLLERR);
+		break;
 	default:
 		return NOTIFY_DONE;
 	}

@@ -2761,4 +2770,6 @@ int gpiolib_cdev_register(struct gpio_device *gdev, dev_t devt)
 void gpiolib_cdev_unregister(struct gpio_device *gdev)
 {
 	cdev_device_del(&gdev->chrdev, &gdev->dev);
+	blocking_notifier_call_chain(&gdev->notifier,
+				     GPIO_CDEV_UNREGISTERED, NULL);
 }

index eb8c0cb71da4..0b21ea04fa52 100644
@@ -563,6 +563,7 @@ struct line {
  * @wait: wait queue that handles blocking reads of events
  * @event_buffer_size: the number of elements allocated in @events
  * @events: KFIFO for the GPIO events
+ * @nb: notifier block for receiving gpio_device notifications
  * @seqno: the sequence number for edge events generated on all lines in
  * this line request.  Note that this is not used when @num_lines is 1, as
  * the line_seqno is then the same and is cheaper to calculate.

@@ -577,11 +578,17 @@ struct linereq {
 	wait_queue_head_t wait;
 	u32 event_buffer_size;
 	DECLARE_KFIFO_PTR(events, struct gpio_v2_line_event);
+	struct notifier_block nb;
 	atomic_t seqno;
 	struct mutex config_mutex;
 	struct line lines[];
 };
 
+static struct linereq *to_linereq(struct notifier_block *nb)
+{
+	return container_of(nb, struct linereq, nb);
+}
+
 #define GPIO_V2_LINE_BIAS_FLAGS \
 	(GPIO_V2_LINE_FLAG_BIAS_PULL_UP | \
 	 GPIO_V2_LINE_FLAG_BIAS_PULL_DOWN | \

@@ -1573,6 +1580,10 @@ static void linereq_free(struct linereq *lr)
 {
 	unsigned int i;
 
+	if (lr->nb.notifier_call)
+		blocking_notifier_chain_unregister(&lr->gdev->notifier,
+						   &lr->nb);
+
 	for (i = 0; i < lr->num_lines; i++) {
 		if (lr->lines[i].desc) {
 			edge_detector_stop(&lr->lines[i]);

@@ -1623,6 +1634,22 @@ static const struct file_operations line_fileops = {
 #endif
 };
 
+static int linereq_notify(struct notifier_block *nb, unsigned long action,
+			  void *data)
+{
+	struct linereq *lr = to_linereq(nb);
+
+	switch (action) {
+	case GPIO_CDEV_UNREGISTERED:
+		wake_up_poll(&lr->wait, EPOLLIN | EPOLLERR);
+		break;
+	default:
+		return NOTIFY_DONE;
+	}
+
+	return NOTIFY_OK;
+}
+
 static int linereq_create(struct gpio_device *gdev, void __user *ip)
 {
 	struct gpio_v2_line_request ulr;

@@ -1733,6 +1760,11 @@ static int linereq_create(struct gpio_device *gdev, void __user *ip)
 			offset);
 	}
 
+	lr->nb.notifier_call = linereq_notify;
+	ret = blocking_notifier_chain_register(&gdev->notifier, &lr->nb);
+	if (ret)
+		goto out_free_linereq;
+
 	fd = get_unused_fd_flags(O_RDONLY | O_CLOEXEC);
 	if (fd < 0) {
 		ret = fd;

index 0b21ea04fa52..bb6a011f7857 100644
@@ -1830,9 +1830,15 @@ struct lineevent_state {
 	int irq;
 	wait_queue_head_t wait;
 	DECLARE_KFIFO(events, struct gpioevent_data, 16);
+	struct notifier_block nb;
 	u64 timestamp;
 };
 
+static struct lineevent_state *to_lineevent_state(struct notifier_block *nb)
+{
+	return container_of(nb, struct lineevent_state, nb);
+}
+
 #define GPIOEVENT_REQUEST_VALID_FLAGS \
 	(GPIOEVENT_REQUEST_RISING_EDGE | \
 	GPIOEVENT_REQUEST_FALLING_EDGE)

@@ -1947,6 +1953,9 @@ static ssize_t lineevent_read(struct file *file, char __user *buf,
 
 static void lineevent_free(struct lineevent_state *le)
 {
+	if (le->nb.notifier_call)
+		blocking_notifier_chain_unregister(&le->gdev->notifier,
+						   &le->nb);
 	if (le->irq)
 		free_irq(le->irq, le);
 	if (le->desc)

@@ -2084,6 +2093,22 @@ static irqreturn_t lineevent_irq_handler(int irq, void *p)
 	return IRQ_WAKE_THREAD;
 }
 
+static int lineevent_notify(struct notifier_block *nb, unsigned long action,
+			    void *data)
+{
+	struct lineevent_state *le = to_lineevent_state(nb);
+
+	switch (action) {
+	case GPIO_CDEV_UNREGISTERED:
+		wake_up_poll(&le->wait, EPOLLIN | EPOLLERR);
+		break;
+	default:
+		return NOTIFY_DONE;
+	}
+
+	return NOTIFY_OK;
+}
+
 static int lineevent_create(struct gpio_device *gdev, void __user *ip)
 {
 	struct gpioevent_request eventreq;

@@ -2175,6 +2200,11 @@ static int lineevent_create(struct gpio_device *gdev, void __user *ip)
 	INIT_KFIFO(le->events);
 	init_waitqueue_head(&le->wait);
 
+	le->nb.notifier_call = lineevent_notify;
+	ret = blocking_notifier_chain_register(&gdev->notifier, &le->nb);
+	if (ret)
+		goto out_free_le;
+
 	/* Request a thread to read the events */
 	ret = request_threaded_irq(irq,
 				   lineevent_irq_handler,