linux-kernel - Re: [RFC PATCH 2/5] iio: kfifo-buffer: Add output buffer support

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Date:   Sun, 14 Feb 2021 16:23:45 +0000
From:   Jonathan Cameron <jic23@...nel.org>
To:     Alexandru Ardelean <alexandru.ardelean@...log.com>
Cc:     <linux-kernel@...r.kernel.org>, <linux-iio@...r.kernel.org>,
        <lars@...afoo.de>, <Michael.Hennerich@...log.com>,
        <nuno.sa@...log.com>, <dragos.bogdan@...log.com>
Subject: Re: [RFC PATCH 2/5] iio: kfifo-buffer: Add output buffer support

On Fri, 12 Feb 2021 12:20:18 +0200
Alexandru Ardelean <alexandru.ardelean@...log.com> wrote:

> From: Lars-Peter Clausen <lars@...afoo.de>
> 
> Add output buffer support to the kfifo buffer implementation.
> 
> The implementation is straight forward and mostly just wraps the kfifo
> API to provide the required operations.
> 
> Signed-off-by: Lars-Peter Clausen <lars@...afoo.de>
> Signed-off-by: Alexandru Ardelean <alexandru.ardelean@...log.com>
Nice.  For some reason I thought it would be more complex than this :)

Jonathan

> ---
>  drivers/iio/buffer/kfifo_buf.c | 50 ++++++++++++++++++++++++++++++++++
>  1 file changed, 50 insertions(+)
> 
> diff --git a/drivers/iio/buffer/kfifo_buf.c b/drivers/iio/buffer/kfifo_buf.c
> index 1359abed3b31..6e055176f969 100644
> --- a/drivers/iio/buffer/kfifo_buf.c
> +++ b/drivers/iio/buffer/kfifo_buf.c
> @@ -138,10 +138,60 @@ static void iio_kfifo_buffer_release(struct iio_buffer *buffer)
>  	kfree(kf);
>  }
>  
> +static size_t iio_kfifo_buf_space_available(struct iio_buffer *r)
> +{
> +	struct iio_kfifo *kf = iio_to_kfifo(r);
> +	size_t avail;
> +
> +	mutex_lock(&kf->user_lock);
> +	avail = kfifo_avail(&kf->kf);
> +	mutex_unlock(&kf->user_lock);
> +
> +	return avail;
> +}
> +
> +static int iio_kfifo_remove_from(struct iio_buffer *r, void *data)
> +{
> +	int ret;
> +	struct iio_kfifo *kf = iio_to_kfifo(r);
> +
> +	if (kfifo_size(&kf->kf) < r->bytes_per_datum)
> +		return -EBUSY;
> +
> +	ret = kfifo_out(&kf->kf, data, r->bytes_per_datum);
> +	if (ret != r->bytes_per_datum)
> +		return -EBUSY;
> +
> +	wake_up_interruptible_poll(&r->pollq, POLLOUT | POLLWRNORM);
> +
> +	return 0;
> +}
> +
> +static int iio_kfifo_write(struct iio_buffer *r, size_t n,
> +	const char __user *buf)
> +{
> +	struct iio_kfifo *kf = iio_to_kfifo(r);
> +	int ret, copied;
> +
> +	mutex_lock(&kf->user_lock);
> +	if (!kfifo_initialized(&kf->kf) || n < kfifo_esize(&kf->kf))
> +		ret = -EINVAL;
> +	else
> +		ret = kfifo_from_user(&kf->kf, buf, n, &copied);
> +	mutex_unlock(&kf->user_lock);
> +	if (ret)
> +		return ret;
> +
> +	return copied;
> +}
> +
>  static const struct iio_buffer_access_funcs kfifo_access_funcs = {
>  	.store_to = &iio_store_to_kfifo,
>  	.read = &iio_read_kfifo,
>  	.data_available = iio_kfifo_buf_data_available,
> +	.remove_from = &iio_kfifo_remove_from,
> +	.write = &iio_kfifo_write,
> +	.space_available = &iio_kfifo_buf_space_available,
>  	.request_update = &iio_request_update_kfifo,
>  	.set_bytes_per_datum = &iio_set_bytes_per_datum_kfifo,
>  	.set_length = &iio_set_length_kfifo,