On 11/25/13 14:56, Lars-Peter Clausen wrote:
> This patch adds a new data_available() callback to the iio_buffer_access_funcs
> struct. The callback is used to indicate whether data is available in the buffer
> for reading. It is meant to replace the stufftoread flag from the iio_buffer
> struct. The reasoning for this is that the buffer implementation usually can
> determine whether data is available rather easily based on its state, on the
> other hand it can be rather tricky to update the stufftoread flag in a race free
> way.
>
> Signed-off-by: Lars-Peter Clausen <lars@xxxxxxxxxx>
A sensible change - applied to the togreg branch of iio.git.
> ---
> drivers/iio/industrialio-buffer.c | 10 +++++++++-
> include/linux/iio/buffer.h | 3 +++
> 2 files changed, 12 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/iio/industrialio-buffer.c b/drivers/iio/industrialio-buffer.c
> index 7f9152c..4dcc3a0 100644
> --- a/drivers/iio/industrialio-buffer.c
> +++ b/drivers/iio/industrialio-buffer.c
> @@ -37,6 +37,14 @@ static bool iio_buffer_is_active(struct iio_buffer *buf)
> return !list_empty(&buf->buffer_list);
> }
>
> +static bool iio_buffer_data_available(struct iio_buffer *buf)
> +{
> + if (buf->access->data_available)
> + return buf->access->data_available(buf);
> +
> + return buf->stufftoread;
> +}
> +
> /**
> * iio_buffer_read_first_n_outer() - chrdev read for buffer access
> *
> @@ -70,7 +78,7 @@ unsigned int iio_buffer_poll(struct file *filp,
> return -ENODEV;
>
> poll_wait(filp, &rb->pollq, wait);
> - if (rb->stufftoread)
> + if (iio_buffer_data_available(rb))
> return POLLIN | POLLRDNORM;
> /* need a way of knowing if there may be enough data... */
> return 0;
> diff --git a/include/linux/iio/buffer.h b/include/linux/iio/buffer.h
> index 15607b4..5193927 100644
> --- a/include/linux/iio/buffer.h
> +++ b/include/linux/iio/buffer.h
> @@ -21,6 +21,8 @@ struct iio_buffer;
> * struct iio_buffer_access_funcs - access functions for buffers.
> * @store_to: actually store stuff to the buffer
> * @read_first_n: try to get a specified number of bytes (must exist)
> + * @data_available: indicates whether data for reading from the buffer is
> + * available.
> * @request_update: if a parameter change has been marked, update underlying
> * storage.
> * @get_bytes_per_datum:get current bytes per datum
> @@ -43,6 +45,7 @@ struct iio_buffer_access_funcs {
> int (*read_first_n)(struct iio_buffer *buffer,
> size_t n,
> char __user *buf);
> + bool (*data_available)(struct iio_buffer *buffer);
>
> int (*request_update)(struct iio_buffer *buffer);
>
>
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