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Date:	Sat, 18 Oct 2014 12:42:37 +0100
From:	Jonathan Cameron <jic23@...nel.org>
To:	"Ivan T. Ivanov" <iivanov@...sol.com>
CC:	Lars-Peter Clausen <lars@...afoo.de>,
	Sachin Kamat <sachin.kamat@...aro.org>,
	Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>,
	John Stultz <john.stultz@...aro.org>,
	linux-iio@...r.kernel.org, svarbanov@...sol.com,
	linux-kernel@...r.kernel.org, linux-arm-msm@...r.kernel.org
Subject: Re: [PATCH] iio: inkern: Add of_xlate function to struct iio_dev

On 02/10/14 13:32, Ivan T. Ivanov wrote:
> When #iio-cells is greater than '0', the driver could provide
> a custom of_xlate function that reads the *args* and returns
> the appropriate index in registered IIO channels array.
> 
> Add simple translation function, suitable for the most 1:1
> mapped channels in IIO chips, and use it when driver did not
> provide custom implementation.
> 
> Signed-off-by: Ivan T. Ivanov <iivanov@...sol.com>
Any more comments on this?  Been sat a while and the discussions seems
to have died out.

As Ivan has pointed out, very similar approaches are used
elsewhere (gpio for example).

> ---
>  drivers/iio/inkern.c    | 32 +++++++++++++++++++++++++++-----
>  include/linux/iio/iio.h |  8 ++++++++
>  2 files changed, 35 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/iio/inkern.c b/drivers/iio/inkern.c
> index f084610..6c3e478 100644
> --- a/drivers/iio/inkern.c
> +++ b/drivers/iio/inkern.c
> @@ -100,6 +100,28 @@ static int iio_dev_node_match(struct device *dev, void *data)
>  	return dev->of_node == data && dev->type == &iio_device_type;
>  }
>  
> +/**
> + * __of_iio_simple_xlate - translate iiospec to the IIO channel index
> + * @indio_dev:	pointer to the iio_dev structure
> + * @iiospec:	IIO specifier as found in the device tree
> + *
> + * This is simple translation function, suitable for the most 1:1 mapped
> + * channels in IIO chips. This function performs only one sanity check:
> + * whether IIO index is less than num_channels (that is specified in the
> + * iio_dev).
> + */
> +static int __of_iio_simple_xlate(struct iio_dev *indio_dev,
> +				const struct of_phandle_args *iiospec)
> +{
> +	if (!iiospec->args_count)
> +		return 0;
> +
> +	if (iiospec->args[0] >= indio_dev->num_channels)
> +		return -EINVAL;
> +
> +	return iiospec->args[0];
> +}
> +
>  static int __of_iio_channel_get(struct iio_channel *channel,
>  				struct device_node *np, int index)
>  {
> @@ -122,18 +144,18 @@ static int __of_iio_channel_get(struct iio_channel *channel,
>  
>  	indio_dev = dev_to_iio_dev(idev);
>  	channel->indio_dev = indio_dev;
> -	index = iiospec.args_count ? iiospec.args[0] : 0;
> -	if (index >= indio_dev->num_channels) {
> -		err = -EINVAL;
> +	if (!indio_dev->of_xlate)
> +		indio_dev->of_xlate = __of_iio_simple_xlate;
> +	index = indio_dev->of_xlate(indio_dev, &iiospec);
> +	if (index < 0)
>  		goto err_put;
> -	}
>  	channel->channel = &indio_dev->channels[index];
>  
>  	return 0;
>  
>  err_put:
>  	iio_device_put(indio_dev);
> -	return err;
> +	return index;
>  }
>  
>  static struct iio_channel *of_iio_channel_get(struct device_node *np, int index)
> diff --git a/include/linux/iio/iio.h b/include/linux/iio/iio.h
> index 15dc6bc..d5bb219 100644
> --- a/include/linux/iio/iio.h
> +++ b/include/linux/iio/iio.h
> @@ -13,6 +13,7 @@
>  #include <linux/device.h>
>  #include <linux/cdev.h>
>  #include <linux/iio/types.h>
> +#include <linux/of.h>
>  /* IIO TODO LIST */
>  /*
>   * Provide means of adjusting timer accuracy.
> @@ -413,6 +414,11 @@ struct iio_buffer_setup_ops {
>   * @currentmode:	[DRIVER] current operating mode
>   * @dev:		[DRIVER] device structure, should be assigned a parent
>   *			and owner
> + * @of_xlate:		[DRIVER] function pointer to obtain channel specifier
> + *			index. When #iio-cells is greater than '0', the driver
> + *			could provide a custom of_xlate function that reads
> + *			the *args* and returns the appropriate index in
> + *			registered IIO channels array.
>   * @event_interface:	[INTERN] event chrdevs associated with interrupt lines
>   * @buffer:		[DRIVER] any buffer present
>   * @buffer_list:	[INTERN] list of all buffers currently attached
> @@ -451,6 +457,8 @@ struct iio_dev {
>  	int				currentmode;
>  	struct device			dev;
>  
> +	int (*of_xlate)(struct iio_dev *indio_dev,
> +			const struct of_phandle_args *iiospec);
>  	struct iio_event_interface	*event_interface;
>  
>  	struct iio_buffer		*buffer;
> 
--
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