Re: [PATCH] iio: buffer-dma: Expose data available

[Jonathan Cameron <jic23@jic23.retrosnub.co.uk>]

On Fri,  1 Dec 2017 15:46:20 -0500
mfornero@gmail.com wrote:

> From: Matt Fornero <matt.fornero@mathworks.com>
> 
> Add a sysfs attribute that exposes the buffer data available to
> userspace. This attribute can be checked at runtime to determine the
> overall buffer fill level (across all allocated DMA buffers).
> 
> Signed-off-by: Matt Fornero <matt.fornero@mathworks.com>

Seems sensible to me.

Lars?

Thanks,

Jonathan
> ---
>  drivers/iio/buffer/industrialio-buffer-dma.c | 24 ++++++++++++++++++++++++
>  1 file changed, 24 insertions(+)
> 
> diff --git a/drivers/iio/buffer/industrialio-buffer-dma.c b/drivers/iio/buffer/industrialio-buffer-dma.c
> index ff03324..8739a41 100644
> --- a/drivers/iio/buffer/industrialio-buffer-dma.c
> +++ b/drivers/iio/buffer/industrialio-buffer-dma.c
> @@ -16,6 +16,7 @@
>  #include <linux/iio/buffer.h>
>  #include <linux/iio/buffer_impl.h>
>  #include <linux/iio/buffer-dma.h>
> +#include <linux/iio/sysfs.h>
>  #include <linux/dma-mapping.h>
>  #include <linux/sizes.h>
>  
> @@ -599,6 +600,28 @@ int iio_dma_buffer_set_length(struct iio_buffer *buffer, int length)
>  }
>  EXPORT_SYMBOL_GPL(iio_dma_buffer_set_length);
>  
> +
> +static ssize_t iio_dma_get_data_available(struct device *dev,
> +					       struct device_attribute *attr,
> +					       char *buf)
> +{
> +	struct iio_dev *indio_dev = dev_to_iio_dev(dev);
> +	size_t bytes;
> +
> +	bytes = iio_dma_buffer_data_available(indio_dev->buffer);
> +
> +	return sprintf(buf, "%llu\n", (unsigned long long)bytes);
> +}
> +
> +static IIO_DEVICE_ATTR(data_available, S_IRUGO,
> +		       iio_dma_get_data_available, NULL, 0);
> +
> +static const struct attribute *iio_dma_buffer_attributes[] = {
> +	&iio_dev_attr_data_available.dev_attr.attr,
> +	NULL,
> +};
> +
> +
>  /**
>   * iio_dma_buffer_init() - Initialize DMA buffer queue
>   * @queue: Buffer to initialize
> @@ -615,6 +638,7 @@ int iio_dma_buffer_init(struct iio_dma_buffer_queue *queue,
>  	iio_buffer_init(&queue->buffer);
>  	queue->buffer.length = PAGE_SIZE;
>  	queue->buffer.watermark = queue->buffer.length / 2;
> +	queue->buffer.attrs = iio_dma_buffer_attributes;
>  	queue->dev = dev;
>  	queue->ops = ops;
>