linux-kernel - Re: [PATCH 2/7] iio: backend: add support for data size set

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Message-ID: <20240928182457.5919be0d@jic23-huawei>
Date: Sat, 28 Sep 2024 18:24:57 +0100
From: Jonathan Cameron <jic23@...nel.org>
To: Antoniu Miclaus <antoniu.miclaus@...log.com>
Cc: Lars-Peter Clausen <lars@...afoo.de>, Michael Hennerich
 <Michael.Hennerich@...log.com>, Rob Herring <robh@...nel.org>, Krzysztof
 Kozlowski <krzk+dt@...nel.org>, Conor Dooley <conor+dt@...nel.org>, Nuno Sa
 <nuno.sa@...log.com>, Olivier Moysan <olivier.moysan@...s.st.com>, Uwe
 Kleine-König <ukleinek@...nel.org>, Andy Shevchenko
 <andy@...nel.org>, David Lechner <dlechner@...libre.com>, Marcelo Schmitt
 <marcelo.schmitt@...log.com>, João Paulo Gonçalves <joao.goncalves@...adex.com>, Dumitru Ceclan
 <mitrutzceclan@...il.com>, AngeloGioacchino Del Regno
 <angelogioacchino.delregno@...labora.com>, Alisa-Dariana Roman
 <alisadariana@...il.com>, Marius Cristea <marius.cristea@...rochip.com>,
 Sergiu Cuciurean <sergiu.cuciurean@...log.com>, Dragos Bogdan
 <dragos.bogdan@...log.com>, <linux-iio@...r.kernel.org>,
 <linux-kernel@...r.kernel.org>, <devicetree@...r.kernel.org>,
 <linux-pwm@...r.kernel.org>
Subject: Re: [PATCH 2/7] iio: backend: add support for data size set

On Mon, 23 Sep 2024 13:10:19 +0300
Antoniu Miclaus <antoniu.miclaus@...log.com> wrote:

> Add backend support for setting the data size used.

Say 'why' a device might do this.  I assume in general
it's because you haven't wired all the pins, but is there a
reason it might be dynamic?

Jonathan

> 
> Signed-off-by: Antoniu Miclaus <antoniu.miclaus@...log.com>
> ---
>  drivers/iio/industrialio-backend.c | 21 +++++++++++++++++++++
>  include/linux/iio/backend.h        |  3 +++
>  2 files changed, 24 insertions(+)
> 
> diff --git a/drivers/iio/industrialio-backend.c b/drivers/iio/industrialio-backend.c
> index 53ab6bc86a50..a6a6bedce7f1 100644
> --- a/drivers/iio/industrialio-backend.c
> +++ b/drivers/iio/industrialio-backend.c
> @@ -473,6 +473,27 @@ int iio_backend_interface_type_get(struct iio_backend *back,
>  }
>  EXPORT_SYMBOL_NS_GPL(iio_backend_interface_type_get, IIO_BACKEND);
>  
> +/**
> + * iio_backend_data_size_set - set the data width/size in the data bus.
> + * @back: Backend device
> + * @size: Size in bits
> + *
> + * Some frontend devices can dynamically control the word/data size on the
> + * interface/data bus. Hence, the backend device needs to be aware of it so
> + * data can be correctly transferred.
> + *
> + * RETURNS:
> + * 0 on success, negative error number on failure.
> + */
> +ssize_t iio_backend_data_size_set(struct iio_backend *back, ssize_t size)
> +{
> +	if (!size)
> +		return -EINVAL;
> +
> +	return iio_backend_op_call(back, data_size_set, size);
> +}
> +EXPORT_SYMBOL_NS_GPL(iio_backend_data_size_set, IIO_BACKEND);
> +
>  /**
>   * iio_backend_extend_chan_spec - Extend an IIO channel
>   * @indio_dev: IIO device
> diff --git a/include/linux/iio/backend.h b/include/linux/iio/backend.h
> index ba8ad30ac9ba..85b33ed69cc0 100644
> --- a/include/linux/iio/backend.h
> +++ b/include/linux/iio/backend.h
> @@ -87,6 +87,7 @@ enum iio_backend_interface_type {
>   * @ext_info_set: Extended info setter.
>   * @ext_info_get: Extended info getter.
>   * @interface_type_get: Interface type.
> + * @data_size_set: Data size.
>   **/
>  struct iio_backend_ops {
>  	int (*enable)(struct iio_backend *back);
> @@ -121,6 +122,7 @@ struct iio_backend_ops {
>  			    const struct iio_chan_spec *chan, char *buf);
>  	int (*interface_type_get)(struct iio_backend *back,
>  				  enum iio_backend_interface_type *type);
> +	int (*data_size_set)(struct iio_backend *back, ssize_t size);
>  };
>  
>  int iio_backend_chan_enable(struct iio_backend *back, unsigned int chan);
> @@ -152,6 +154,7 @@ ssize_t iio_backend_ext_info_get(struct iio_dev *indio_dev, uintptr_t private,
>  
>  int iio_backend_interface_type_get(struct iio_backend *back,
>  				   enum iio_backend_interface_type *type);
> +ssize_t iio_backend_data_size_set(struct iio_backend *back, ssize_t size);
>  int iio_backend_extend_chan_spec(struct iio_dev *indio_dev,
>  				 struct iio_backend *back,
>  				 struct iio_chan_spec *chan);