linux-kernel - Re: [PATCH 13/15] iio: core: Add support for cyclic buffers

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Date:   Tue, 16 Nov 2021 11:50:03 +0200
From:   Alexandru Ardelean <ardeleanalex@...il.com>
To:     Paul Cercueil <paul@...pouillou.net>
Cc:     Jonathan Cameron <jic23@...nel.org>,
        Lars-Peter Clausen <lars@...afoo.de>,
        Michael Hennerich <Michael.Hennerich@...log.com>,
        Sumit Semwal <sumit.semwal@...aro.org>,
        Christian König <christian.koenig@....com>,
        linux-iio <linux-iio@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>, linux-media@...r.kernel.org,
        dri-devel@...ts.freedesktop.org, linaro-mm-sig@...ts.linaro.org
Subject: Re: [PATCH 13/15] iio: core: Add support for cyclic buffers

On Mon, Nov 15, 2021 at 4:22 PM Paul Cercueil <paul@...pouillou.net> wrote:
>
> Introduce a new flag IIO_BUFFER_DMABUF_CYCLIC in the "flags" field of
> the iio_dmabuf uapi structure.
>
> When set, the DMABUF enqueued with the enqueue ioctl will be endlessly
> repeated on the TX output, until the buffer is disabled.
>

Reviewed-by: Alexandru Ardelean <ardeleanalex@...il.com>

> Signed-off-by: Paul Cercueil <paul@...pouillou.net>
> ---
>  drivers/iio/industrialio-buffer.c | 5 +++++
>  include/uapi/linux/iio/buffer.h   | 3 ++-
>  2 files changed, 7 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/iio/industrialio-buffer.c b/drivers/iio/industrialio-buffer.c
> index 30910e6c2346..41bc51c88002 100644
> --- a/drivers/iio/industrialio-buffer.c
> +++ b/drivers/iio/industrialio-buffer.c
> @@ -1600,6 +1600,11 @@ static int iio_buffer_enqueue_dmabuf(struct iio_buffer *buffer,
>         if (dmabuf.flags & ~IIO_BUFFER_DMABUF_SUPPORTED_FLAGS)
>                 return -EINVAL;
>
> +       /* Cyclic flag is only supported on output buffers */
> +       if ((dmabuf.flags & IIO_BUFFER_DMABUF_CYCLIC) &&
> +           buffer->direction != IIO_BUFFER_DIRECTION_OUT)
> +               return -EINVAL;
> +
>         return buffer->access->enqueue_dmabuf(buffer, &dmabuf);
>  }
>
> diff --git a/include/uapi/linux/iio/buffer.h b/include/uapi/linux/iio/buffer.h
> index e4621b926262..2d541d038c02 100644
> --- a/include/uapi/linux/iio/buffer.h
> +++ b/include/uapi/linux/iio/buffer.h
> @@ -7,7 +7,8 @@
>
>  #include <linux/types.h>
>
> -#define IIO_BUFFER_DMABUF_SUPPORTED_FLAGS      0x00000000
> +#define IIO_BUFFER_DMABUF_CYCLIC               (1 << 0)
> +#define IIO_BUFFER_DMABUF_SUPPORTED_FLAGS      0x00000001
>
>  /**
>   * struct iio_dmabuf_alloc_req - Descriptor for allocating IIO DMABUFs
> --
> 2.33.0
>