Re: [PATCH 3/3] iio: Add support for blocking IO on buffers

[Jonathan Cameron <jic23@kernel.org>]

On 11/25/13 14:56, Lars-Peter Clausen wrote:
> Currently the IIO buffer interface only allows non-blocking reads. This patch
> adds support for blocking IO. In blocking mode the thread will go to sleep if no
> data is available and will wait for the buffer implementation to signal that new
> data is available by waking up the buffers waitqueue.
> 
> Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Applied to the togreg branch of iio.git

Nice little bit of functionality. Thanks.

Jonathan
> ---
>  drivers/iio/industrialio-buffer.c | 23 ++++++++++++++++++++++-
>  1 file changed, 22 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/iio/industrialio-buffer.c b/drivers/iio/industrialio-buffer.c
> index 4dcc3a0..c67d83b 100644
> --- a/drivers/iio/industrialio-buffer.c
> +++ b/drivers/iio/industrialio-buffer.c
> @@ -56,13 +56,34 @@ ssize_t iio_buffer_read_first_n_outer(struct file *filp, char __user *buf,
>  {
>  	struct iio_dev *indio_dev = filp->private_data;
>  	struct iio_buffer *rb = indio_dev->buffer;
> +	int ret;
>  
>  	if (!indio_dev->info)
>  		return -ENODEV;
>  
>  	if (!rb || !rb->access->read_first_n)
>  		return -EINVAL;
> -	return rb->access->read_first_n(rb, n, buf);
> +
> +	do {
> +		if (!iio_buffer_data_available(rb)) {
> +			if (filp->f_flags & O_NONBLOCK)
> +				return -EAGAIN;
> +
> +			ret = wait_event_interruptible(rb->pollq,
> +					iio_buffer_data_available(rb) ||
> +					indio_dev->info == NULL);
> +			if (ret)
> +				return ret;
> +			if (indio_dev->info == NULL)
> +				return -ENODEV;
> +		}
> +
> +		ret = rb->access->read_first_n(rb, n, buf);
> +		if (ret == 0 && (filp->f_flags & O_NONBLOCK))
> +			ret = -EAGAIN;
> +	 } while (ret == 0);
> +
> +	return ret;
>  }
>  
>  /**
>