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Message-Id: <20230816122032.15548-6-brgl@bgdev.pl>
Date: Wed, 16 Aug 2023 14:20:32 +0200
From: Bartosz Golaszewski <brgl@...ev.pl>
To: Linus Walleij <linus.walleij@...aro.org>,
Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
Kent Gibson <warthog618@...il.com>
Cc: linux-gpio@...r.kernel.org, linux-kernel@...r.kernel.org,
Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
Subject: [PATCH 5/5] gpio: cdev: wake up lineevent poll() on device unbind
From: Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
Extend struct lineevent_data with a notifier block and use it to receive
the GPIO device unregister event. Upon reception, wake up the wait queue
so that the user-space be forced out of poll() and need to go into a new
system call which will then fail due to the chip being gone.
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
---
drivers/gpio/gpiolib-cdev.c | 30 ++++++++++++++++++++++++++++++
1 file changed, 30 insertions(+)
diff --git a/drivers/gpio/gpiolib-cdev.c b/drivers/gpio/gpiolib-cdev.c
index 0b21ea04fa52..bb6a011f7857 100644
--- a/drivers/gpio/gpiolib-cdev.c
+++ b/drivers/gpio/gpiolib-cdev.c
@@ -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,
--
2.39.2
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