linux-kernel - Re: [PATCH 1/7] iio: backend: add API for interface get

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Message-ID: <CAMknhBHmtpnX-nXxReF-rUW1ks1=iw3m_BmiRUTkf5XckPsvPw@mail.gmail.com>
Date: Thu, 26 Sep 2024 10:40:25 +0200
From: David Lechner <dlechner@...libre.com>
To: Antoniu Miclaus <antoniu.miclaus@...log.com>
Cc: Jonathan Cameron <jic23@...nel.org>, 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>, Marcelo Schmitt <marcelo.schmitt@...log.com>, 
	Alisa-Dariana Roman <alisadariana@...il.com>, 
	AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>, 
	Dumitru Ceclan <mitrutzceclan@...il.com>, 
	João Paulo Gonçalves <joao.goncalves@...adex.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 1/7] iio: backend: add API for interface get

On Mon, Sep 23, 2024 at 12:15 PM Antoniu Miclaus
<antoniu.miclaus@...log.com> wrote:
>
> Add backend support for obtaining the interface type used.
>
> Signed-off-by: Antoniu Miclaus <antoniu.miclaus@...log.com>
> ---
>  drivers/iio/industrialio-backend.c | 24 ++++++++++++++++++++++++
>  include/linux/iio/backend.h        | 10 ++++++++++
>  2 files changed, 34 insertions(+)
>
> diff --git a/drivers/iio/industrialio-backend.c b/drivers/iio/industrialio-backend.c
> index efe05be284b6..53ab6bc86a50 100644
> --- a/drivers/iio/industrialio-backend.c
> +++ b/drivers/iio/industrialio-backend.c
> @@ -449,6 +449,30 @@ ssize_t iio_backend_ext_info_set(struct iio_dev *indio_dev, uintptr_t private,
>  }
>  EXPORT_SYMBOL_NS_GPL(iio_backend_ext_info_set, IIO_BACKEND);
>
> +/**
> + * iio_backend_interface_type_get - get the interace type used.
> + * @back: Backend device
> + * @type: Interface type
> + *
> + * RETURNS:
> + * 0 on success, negative error number on failure.
> + */
> +int iio_backend_interface_type_get(struct iio_backend *back,
> +                                  enum iio_backend_interface_type *type)
> +{
> +       int ret;
> +
> +       ret = iio_backend_op_call(back, interface_type_get, type);
> +       if (ret)
> +               return ret;
> +
> +       if (*type > IIO_BACKEND_INTERFACE_CMOS)
> +               return -EINVAL;
> +
> +       return 0;
> +}
> +EXPORT_SYMBOL_NS_GPL(iio_backend_interface_type_get, 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 8099759d7242..ba8ad30ac9ba 100644
> --- a/include/linux/iio/backend.h
> +++ b/include/linux/iio/backend.h
> @@ -63,6 +63,11 @@ enum iio_backend_sample_trigger {
>         IIO_BACKEND_SAMPLE_TRIGGER_MAX
>  };
>
> +enum iio_backend_interface_type {
> +       IIO_BACKEND_INTERFACE_LVDS,
> +       IIO_BACKEND_INTERFACE_CMOS
> +};
> +
>  /**
>   * struct iio_backend_ops - operations structure for an iio_backend
>   * @enable: Enable backend.
> @@ -81,6 +86,7 @@ enum iio_backend_sample_trigger {
>   * @extend_chan_spec: Extend an IIO channel.
>   * @ext_info_set: Extended info setter.
>   * @ext_info_get: Extended info getter.
> + * @interface_type_get: Interface type.
>   **/
>  struct iio_backend_ops {
>         int (*enable)(struct iio_backend *back);
> @@ -113,6 +119,8 @@ struct iio_backend_ops {
>                             const char *buf, size_t len);
>         int (*ext_info_get)(struct iio_backend *back, uintptr_t private,
>                             const struct iio_chan_spec *chan, char *buf);
> +       int (*interface_type_get)(struct iio_backend *back,
> +                                 enum iio_backend_interface_type *type);
>  };
>
>  int iio_backend_chan_enable(struct iio_backend *back, unsigned int chan);
> @@ -142,6 +150,8 @@ ssize_t iio_backend_ext_info_set(struct iio_dev *indio_dev, uintptr_t private,
>  ssize_t iio_backend_ext_info_get(struct iio_dev *indio_dev, uintptr_t private,
>                                  const struct iio_chan_spec *chan, char *buf);
>
> +int iio_backend_interface_type_get(struct iio_backend *back,
> +                                  enum iio_backend_interface_type *type);
>  int iio_backend_extend_chan_spec(struct iio_dev *indio_dev,
>                                  struct iio_backend *back,
>                                  struct iio_chan_spec *chan);
> --
> 2.46.0
>

This seems very specific to the AD485x chips and the AXI ADC backend.
Since it is describing how the chip is wired to the AXI DAC IP block,
I would be tempted to use the devicetree for this info instead of
adding a new backend function.