Re: [PATCH 01/24] iio: Add iio_push_buffers_with_timestamp() helper

[Jonathan Cameron <jic23@kernel.org>]

On 09/19/13 13:59, Lars-Peter Clausen wrote:
> Drivers using software buffers often store the timestamp in their data buffer
> before calling iio_push_to_buffers() with that data buffer. Storing the
> timestamp in the buffer usually involves some ugly pointer arithmetic. This
> patch adds a new helper function called iio_push_buffers_with_timestamp() which
> is similar to iio_push_to_buffers but takes an additional timestamp parameter.
> The function will help to hide to uglyness in one central place instead of
> exposing it in every driver. If timestamps are enabled for the IIO device
> iio_push_buffers_with_timestamp() will store the timestamp as the last element
> in buffer, before passing the buffer on to iio_push_buffers(). The buffer needs
> large enough to hold the timestamp in this case. If timestamps are disabled
> iio_push_buffers_with_timestamp() will behave just like iio_push_buffers().
> 
> Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
> Cc: Oleksandr Kravchenko <o.v.kravchenko@globallogic.com>
> Cc: Josh Wu <josh.wu@atmel.com>
> Cc: Denis Ciocca <denis.ciocca@gmail.com>
> Cc: Manuel Stahl <manuel.stahl@iis.fraunhofer.de>
> Cc: Ge Gao <ggao@invensense.com>
> Cc: Peter Meerwald <pmeerw@pmeerw.net>
> Cc: Jacek Anaszewski <j.anaszewski@samsung.com>
> Cc: Fabio Estevam <fabio.estevam@freescale.com>
> Cc: Marek Vasut <marex@denx.de>
Applied to the togreg branch of iio.git

Thanks
> ---
>  include/linux/iio/buffer.h | 25 +++++++++++++++++++++++++
>  1 file changed, 25 insertions(+)
> 
> diff --git a/include/linux/iio/buffer.h b/include/linux/iio/buffer.h
> index e5507e9..a1124bd 100644
> --- a/include/linux/iio/buffer.h
> +++ b/include/linux/iio/buffer.h
> @@ -122,6 +122,31 @@ int iio_scan_mask_set(struct iio_dev *indio_dev,
>   */
>  int iio_push_to_buffers(struct iio_dev *indio_dev, const void *data);
>  
> +/*
> + * iio_push_to_buffers_with_timestamp() - push data and timestamp to buffers
> + * @indio_dev:		iio_dev structure for device.
> + * @data:		sample data
> + * @timestamp:		timestamp for the sample data
> + *
> + * Pushes data to the IIO device's buffers. If timestamps are enabled for the
> + * device the function will store the supplied timestamp as the last element in
> + * the sample data buffer before pushing it to the device buffers. The sample
> + * data buffer needs to be large enough to hold the additional timestamp
> + * (usually the buffer should be indio->scan_bytes bytes large).
> + *
> + * Returns 0 on success, a negative error code otherwise.
> + */
> +static inline int iio_push_to_buffers_with_timestamp(struct iio_dev *indio_dev,
> +	void *data, int64_t timestamp)
> +{
> +	if (indio_dev->scan_timestamp) {
> +		size_t ts_offset = indio_dev->scan_bytes / sizeof(int64_t) - 1;
> +		((int64_t *)data)[ts_offset] = timestamp;
> +	}
> +
> +	return iio_push_to_buffers(indio_dev, data);
> +}
> +
>  int iio_update_demux(struct iio_dev *indio_dev);
>  
>  /**
>