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gpio: cdev: wake up lineevent poll() on device unbind

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Add a notifier block to the lineevent_state structure and register it
with the gpio_device's device notifier. Upon reception of an event, 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@linaro.org>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Reviewed-by: Kent Gibson <warthog618@gmail.com>
This commit is contained in:
Bartosz Golaszewski 2023-08-17 15:28:31 +02:00
parent a0dda508bd
commit 91043f5593
1 changed files with 22 additions and 0 deletions
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22
drivers/gpio/gpiolib-cdev.c
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@ -1802,6 +1802,7 @@ out_free_linereq:
* @eflags: the event flags this line was requested with
* @irq: the interrupt that trigger in response to events on this GPIO
* @wait: wait queue that handles blocking reads of events
* @device_unregistered_nb: notifier block for receiving gdev unregister events
* @events: KFIFO for the GPIO events
* @timestamp: cache for the timestamp storing it between hardirq
* and IRQ thread, used to bring the timestamp close to the actual
@ -1814,6 +1815,7 @@ struct lineevent_state {
u32 eflags;
int irq;
wait_queue_head_t wait;
struct notifier_block device_unregistered_nb;
DECLARE_KFIFO(events, struct gpioevent_data, 16);
u64 timestamp;
};
@ -1847,6 +1849,17 @@ static __poll_t lineevent_poll(struct file *file,
return call_poll_locked(file, wait, le->gdev, lineevent_poll_unlocked);
}
static int lineevent_unregistered_notify(struct notifier_block *nb,
unsigned long action, void *data)
{
struct lineevent_state *le = container_of(nb, struct lineevent_state,
device_unregistered_nb);
wake_up_poll(&le->wait, EPOLLIN | EPOLLERR);
return NOTIFY_OK;
}
struct compat_gpioeevent_data {
compat_u64 timestamp;
u32 id;
@ -1932,6 +1945,9 @@ static ssize_t lineevent_read(struct file *file, char __user *buf,
static void lineevent_free(struct lineevent_state *le)
{
if (le->device_unregistered_nb.notifier_call)
blocking_notifier_chain_unregister(&le->gdev->device_notifier,
&le->device_unregistered_nb);
if (le->irq)
free_irq(le->irq, le);
if (le->desc)
@ -2160,6 +2176,12 @@ static int lineevent_create(struct gpio_device *gdev, void __user *ip)
INIT_KFIFO(le->events);
init_waitqueue_head(&le->wait);
le->device_unregistered_nb.notifier_call = lineevent_unregistered_notify;
ret = blocking_notifier_chain_register(&gdev->device_notifier,
&le->device_unregistered_nb);
if (ret)
goto out_free_le;
/* Request a thread to read the events */
ret = request_threaded_irq(irq,
lineevent_irq_handler,