linux-kernel - Re: [PATCH v3 2/5] iio: buffer: add back-ref from iio_buffer to iio

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Date:   Mon, 13 Apr 2020 16:48:53 +0100
From:   Jonathan Cameron <jic23@...nel.org>
To:     Alexandru Ardelean <alexandru.ardelean@...log.com>
Cc:     <linux-iio@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <lars@...afoo.de>
Subject: Re: [PATCH v3 2/5] iio: buffer: add back-ref from iio_buffer to
 iio_dev

On Fri, 10 Apr 2020 17:17:26 +0300
Alexandru Ardelean <alexandru.ardelean@...log.com> wrote:

> An IIO device will have multiple buffers, but it shouldn't be allowed that
> an IIO buffer should belong to more than 1 IIO device.
> 
> Once things get moved more from IIO device to the IIO buffer, and an IIO
> device will be able to have more than 1 buffer attached, there will be a
> need for a back-ref to the IIO device [from the IIO buffer].
> 
> This change adds that.
> 
> Signed-off-by: Alexandru Ardelean <alexandru.ardelean@...log.com>

Much as I hate circular references, I can't see a way around this one...

> ---
>  drivers/iio/industrialio-buffer.c | 2 ++
>  include/linux/iio/buffer_impl.h   | 3 +++
>  2 files changed, 5 insertions(+)
> 
> diff --git a/drivers/iio/industrialio-buffer.c b/drivers/iio/industrialio-buffer.c
> index e6fa1a4e135d..f9ffc7762f6c 100644
> --- a/drivers/iio/industrialio-buffer.c
> +++ b/drivers/iio/industrialio-buffer.c
> @@ -1478,5 +1478,7 @@ void iio_device_attach_buffer(struct iio_dev *indio_dev,
>  			      struct iio_buffer *buffer)
>  {
>  	indio_dev->buffer = iio_buffer_get(buffer);
> +
> +	indio_dev->buffer->indio_dev = indio_dev;
>  }
>  EXPORT_SYMBOL_GPL(iio_device_attach_buffer);
> diff --git a/include/linux/iio/buffer_impl.h b/include/linux/iio/buffer_impl.h
> index 1e7edf6bed96..8fb92250a190 100644
> --- a/include/linux/iio/buffer_impl.h
> +++ b/include/linux/iio/buffer_impl.h
> @@ -69,6 +69,9 @@ struct iio_buffer_access_funcs {
>   * those writing new buffer implementations.
>   */
>  struct iio_buffer {
> +	/** @indio_dev: IIO device to which this buffer belongs to. */
> +	struct iio_dev *indio_dev;
> +
>  	/** @length: Number of datums in buffer. */
>  	unsigned int length;
>