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

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Add a notifier block to the linereq 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 15:18:58 +02:00
parent d2e2586a32
commit a0dda508bd
1 changed files with 23 additions and 0 deletions
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23
drivers/gpio/gpiolib-cdev.c
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@ -555,6 +555,7 @@ struct line {
* @label: consumer label used to tag GPIO descriptors
* @num_lines: the number of lines in the lines array
* @wait: wait queue that handles blocking reads of events
* @device_unregistered_nb: notifier block for receiving gdev unregister events
* @event_buffer_size: the number of elements allocated in @events
* @events: KFIFO for the GPIO events
* @seqno: the sequence number for edge events generated on all lines in
@ -569,6 +570,7 @@ struct linereq {
const char *label;
u32 num_lines;
wait_queue_head_t wait;
struct notifier_block device_unregistered_nb;
u32 event_buffer_size;
DECLARE_KFIFO_PTR(events, struct gpio_v2_line_event);
atomic_t seqno;
@ -610,6 +612,17 @@ struct linereq {
GPIO_V2_LINE_FLAG_EVENT_CLOCK_HTE | \
GPIO_V2_LINE_EDGE_FLAGS)
static int linereq_unregistered_notify(struct notifier_block *nb,
unsigned long action, void *data)
{
struct linereq *lr = container_of(nb, struct linereq,
device_unregistered_nb);
wake_up_poll(&lr->wait, EPOLLIN | EPOLLERR);
return NOTIFY_OK;
}
static void linereq_put_event(struct linereq *lr,
struct gpio_v2_line_event *le)
{
@ -1567,6 +1580,10 @@ static void linereq_free(struct linereq *lr)
{
unsigned int i;
if (lr->device_unregistered_nb.notifier_call)
blocking_notifier_chain_unregister(&lr->gdev->device_notifier,
&lr->device_unregistered_nb);
for (i = 0; i < lr->num_lines; i++) {
if (lr->lines[i].desc) {
edge_detector_stop(&lr->lines[i]);
@ -1727,6 +1744,12 @@ static int linereq_create(struct gpio_device *gdev, void __user *ip)
offset);
}
lr->device_unregistered_nb.notifier_call = linereq_unregistered_notify;
ret = blocking_notifier_chain_register(&gdev->device_notifier,
&lr->device_unregistered_nb);
if (ret)
goto out_free_linereq;
fd = get_unused_fd_flags(O_RDONLY | O_CLOEXEC);
if (fd < 0) {
ret = fd;