On Wed, 17 Feb 2021 10:34:35 +0200
Alexandru Ardelean <alexandru.ardelean@xxxxxxxxxx> wrote:
> From: Lars-Peter Clausen <lars@xxxxxxxxxx>
>
> Currently IIO only supports buffer mode for capture devices like ADCs. Add
> support for buffered mode for output devices like DACs.
>
> The output buffer implementation is analogous to the input buffer
> implementation. Instead of using read() to get data from the buffer write()
> is used to copy data into the buffer.
>
> poll() with POLLOUT will wakeup if there is space available for more or
> equal to the configured watermark of samples.
>
> Drivers can remove data from a buffer using iio_buffer_remove_sample(), the
> function can e.g. called from a trigger handler to write the data to
> hardware.
>
> A buffer can only be either a output buffer or an input, but not both. So,
> for a device that has an ADC and DAC path, this will mean 2 IIO buffers
> (one for each direction).
>
> The direction of the buffer is decided by the new direction field of the
> iio_buffer struct and should be set after allocating and before registering
> it.
>
> Signed-off-by: Lars-Peter Clausen <lars@xxxxxxxxxx>
> Signed-off-by: Alexandru Ardelean <alexandru.ardelean@xxxxxxxxxx>
Just one question on this, otherwise looks good to me.
Jonathan
> diff --git a/drivers/iio/industrialio-buffer.c b/drivers/iio/industrialio-buffer.c
> index 5d641f8adfbd..b9970c68005d 100644
> --- a/drivers/iio/industrialio-buffer.c
> +++ b/drivers/iio/industrialio-buffer.c
> @@ -162,6 +162,69 @@ static ssize_t iio_buffer_read(struct file *filp, char __user *buf,
> return ret;
> }
>
...
> /**
> * iio_buffer_poll() - poll the buffer to find out if it has data
> * @filp: File structure pointer for device access
> @@ -182,8 +245,19 @@ static __poll_t iio_buffer_poll(struct file *filp,
> return 0;
>
> poll_wait(filp, &rb->pollq, wait);
> - if (iio_buffer_ready(indio_dev, rb, rb->watermark, 0))
> - return EPOLLIN | EPOLLRDNORM;
> +
> + switch (rb->direction) {
> + case IIO_BUFFER_DIRECTION_IN:
> + if (iio_buffer_ready(indio_dev, rb, rb->watermark, 0))
> + return EPOLLIN | EPOLLRDNORM;
> + break;
> + case IIO_BUFFER_DIRECTION_OUT:
> + if (iio_buffer_space_available(rb) >= rb->watermark)
> + return EPOLLOUT | EPOLLWRNORM;
> + break;
> + }
> +
> + /* need a way of knowing if there may be enough data... */
Curious on what this comment is referring to?
> return 0;
> }
>
> @@ -232,6 +306,16 @@ void iio_buffer_wakeup_poll(struct iio_dev *indio_dev)
> }
> }
...
