Re: [PATCH v2 3/5] iio: Wakeup poll and blocking reads when the device is unregistered

[Jonathan Cameron <jic23@kernel.org>]

On 10/04/13 12:07, Lars-Peter Clausen wrote:
> Once the device has been unregistered there won't be any new data no matter how
> long a userspace application waits, so we might as well wake them up and let
> them know.
> 
> Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
I guess this makes sense given they'll then do a read and get an error to indicate
that the device is no longer there.

Applied to the togreg branch of iio.git

Thanks,

Jonathan
> ---
> No changes since v1
> ---
>  drivers/iio/iio_core.h            |  3 +++
>  drivers/iio/industrialio-buffer.c | 16 ++++++++++++++++
>  drivers/iio/industrialio-core.c   |  4 ++++
>  drivers/iio/industrialio-event.c  | 21 ++++++++++++++++++++-
>  4 files changed, 43 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/iio/iio_core.h b/drivers/iio/iio_core.h
> index 9209f47..7512cf7 100644
> --- a/drivers/iio/iio_core.h
> +++ b/drivers/iio/iio_core.h
> @@ -50,6 +50,7 @@ ssize_t iio_buffer_read_first_n_outer(struct file *filp, char __user *buf,
>  #define iio_buffer_read_first_n_outer_addr (&iio_buffer_read_first_n_outer)
>  
>  void iio_disable_all_buffers(struct iio_dev *indio_dev);
> +void iio_buffer_wakeup_poll(struct iio_dev *indio_dev);
>  
>  #else
>  
> @@ -57,11 +58,13 @@ void iio_disable_all_buffers(struct iio_dev *indio_dev);
>  #define iio_buffer_read_first_n_outer_addr NULL
>  
>  static inline void iio_disable_all_buffers(struct iio_dev *indio_dev) {}
> +static inline void iio_buffer_wakeup_poll(struct iio_dev *indio_dev) {}
>  
>  #endif
>  
>  int iio_device_register_eventset(struct iio_dev *indio_dev);
>  void iio_device_unregister_eventset(struct iio_dev *indio_dev);
> +void iio_device_wakeup_eventset(struct iio_dev *indio_dev);
>  int iio_event_getfd(struct iio_dev *indio_dev);
>  
>  #endif
> diff --git a/drivers/iio/industrialio-buffer.c b/drivers/iio/industrialio-buffer.c
> index 6c7a9c5..5a46c57 100644
> --- a/drivers/iio/industrialio-buffer.c
> +++ b/drivers/iio/industrialio-buffer.c
> @@ -20,6 +20,7 @@
>  #include <linux/cdev.h>
>  #include <linux/slab.h>
>  #include <linux/poll.h>
> +#include <linux/sched.h>
>  
>  #include <linux/iio/iio.h>
>  #include "iio_core.h"
> @@ -75,6 +76,21 @@ unsigned int iio_buffer_poll(struct file *filp,
>  	return 0;
>  }
>  
> +/**
> + * iio_buffer_wakeup_poll - Wakes up the buffer waitqueue
> + * @indio_dev: The IIO device
> + *
> + * Wakes up the event waitqueue used for poll(). Should usually
> + * be called when the device is unregistered.
> + */
> +void iio_buffer_wakeup_poll(struct iio_dev *indio_dev)
> +{
> +	if (!indio_dev->buffer)
> +		return;
> +
> +	wake_up(&indio_dev->buffer->pollq);
> +}
> +
>  void iio_buffer_init(struct iio_buffer *buffer)
>  {
>  	INIT_LIST_HEAD(&buffer->demux_list);
> diff --git a/drivers/iio/industrialio-core.c b/drivers/iio/industrialio-core.c
> index c9c6558..81650e1 100644
> --- a/drivers/iio/industrialio-core.c
> +++ b/drivers/iio/industrialio-core.c
> @@ -1139,6 +1139,10 @@ void iio_device_unregister(struct iio_dev *indio_dev)
>  	iio_disable_all_buffers(indio_dev);
>  
>  	indio_dev->info = NULL;
> +
> +	iio_device_wakeup_eventset(indio_dev);
> +	iio_buffer_wakeup_poll(indio_dev);
> +
>  	mutex_unlock(&indio_dev->info_exist_lock);
>  }
>  EXPORT_SYMBOL(iio_device_unregister);
> diff --git a/drivers/iio/industrialio-event.c b/drivers/iio/industrialio-event.c
> index 837d450..d251f30 100644
> --- a/drivers/iio/industrialio-event.c
> +++ b/drivers/iio/industrialio-event.c
> @@ -113,9 +113,14 @@ static ssize_t iio_event_chrdev_read(struct file *filep,
>  		}
>  		/* Blocking on device; waiting for something to be there */
>  		ret = wait_event_interruptible_locked_irq(ev_int->wait,
> -					!kfifo_is_empty(&ev_int->det_events));
> +					!kfifo_is_empty(&ev_int->det_events) ||
> +					indio_dev->info == NULL);
>  		if (ret)
>  			goto error_unlock;
> +		if (indio_dev->info == NULL) {
> +			ret = -ENODEV;
> +			goto error_unlock;
> +		}
>  		/* Single access device so no one else can get the data */
>  	}
>  
> @@ -454,6 +459,20 @@ error_ret:
>  	return ret;
>  }
>  
> +/**
> + * iio_device_wakeup_eventset - Wakes up the event waitqueue
> + * @indio_dev: The IIO device
> + *
> + * Wakes up the event waitqueue used for poll() and blocking read().
> + * Should usually be called when the device is unregistered.
> + */
> +void iio_device_wakeup_eventset(struct iio_dev *indio_dev)
> +{
> +	if (indio_dev->event_interface == NULL)
> +		return;
> +	wake_up(&indio_dev->event_interface->wait);
> +}
> +
>  void iio_device_unregister_eventset(struct iio_dev *indio_dev)
>  {
>  	if (indio_dev->event_interface == NULL)
>