linux-kernel - Re: [PATCH 2/3] staging: iio: cdc: ad7746: use dt bindings to set the EXCx pins output

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Date:   Sat, 10 Apr 2021 19:12:49 +0300
From:   Alexandru Ardelean <ardeleanalex@...il.com>
To:     Lucas Stankus <lucas.p.stankus@...il.com>
Cc:     Lars-Peter Clausen <lars@...afoo.de>,
        "Hennerich, Michael" <Michael.Hennerich@...log.com>,
        Jonathan Cameron <jic23@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-iio <linux-iio@...r.kernel.org>,
        linux-staging@...ts.linux.dev, LKML <linux-kernel@...r.kernel.org>,
        devicetree <devicetree@...r.kernel.org>
Subject: Re: [PATCH 2/3] staging: iio: cdc: ad7746: use dt bindings to set the
 EXCx pins output

On Fri, Apr 9, 2021 at 9:51 PM Lucas Stankus <lucas.p.stankus@...il.com> wrote:
>
> Ditch platform_data fields in favor of device tree properties for
> configuring EXCA and EXCB output.
> This also removes the fields from the platform_data struct, since they're
> not used anymore.
>
> Signed-off-by: Lucas Stankus <lucas.p.stankus@...il.com>
> ---
>  drivers/staging/iio/cdc/ad7746.c | 33 +++++++++++++++++---------------
>  drivers/staging/iio/cdc/ad7746.h |  4 ----
>  2 files changed, 18 insertions(+), 19 deletions(-)
>
> diff --git a/drivers/staging/iio/cdc/ad7746.c b/drivers/staging/iio/cdc/ad7746.c
> index dfd71e99e872..63041b164dbe 100644
> --- a/drivers/staging/iio/cdc/ad7746.c
> +++ b/drivers/staging/iio/cdc/ad7746.c
> @@ -677,8 +677,10 @@ static int ad7746_probe(struct i2c_client *client,
>                         const struct i2c_device_id *id)
>  {
>         struct ad7746_platform_data *pdata = client->dev.platform_data;
> +       struct device_node *np = client->dev.of_node;
>         struct ad7746_chip_info *chip;
>         struct iio_dev *indio_dev;
> +       unsigned int exca_en, excb_en;
>         unsigned char regval = 0;
>         int ret = 0;
>
> @@ -703,26 +705,27 @@ static int ad7746_probe(struct i2c_client *client,
>         indio_dev->num_channels = ARRAY_SIZE(ad7746_channels);
>         indio_dev->modes = INDIO_DIRECT_MODE;
>

[1]

> -       if (pdata) {
> -               if (pdata->exca_en) {
> -                       if (pdata->exca_inv_en)
> -                               regval |= AD7746_EXCSETUP_NEXCA;
> -                       else
> -                               regval |= AD7746_EXCSETUP_EXCA;
> -               }
> +       ret = of_property_read_u32(np, "adi,exca-output", &exca_en);

maybe a better idea would be to use:

device_property_read_u32(dev, .... )
where:
dev = client->dev.;

this would make the driver a bit more friendly with both OF and ACPI

> +       if (!ret && exca_en) {
> +               if (exca_en == 1)
> +                       regval |= AD7746_EXCSETUP_EXCA;
> +               else
> +                       regval |= AD7746_EXCSETUP_NEXCA;
> +       }
>
> -               if (pdata->excb_en) {
> -                       if (pdata->excb_inv_en)
> -                               regval |= AD7746_EXCSETUP_NEXCB;
> -                       else
> -                               regval |= AD7746_EXCSETUP_EXCB;
> -               }
> +       ret = of_property_read_u32(np, "adi,excb-output", &excb_en);
> +       if (!ret && excb_en) {
> +               if (excb_en == 1)
> +                       regval |= AD7746_EXCSETUP_EXCB;
> +               else
> +                       regval |= AD7746_EXCSETUP_NEXCB;
> +       }
>
> +       if (pdata) {
>                 regval |= AD7746_EXCSETUP_EXCLVL(pdata->exclvl);
>         } else {
>                 dev_warn(&client->dev, "No platform data? using default\n");
> -               regval = AD7746_EXCSETUP_EXCA | AD7746_EXCSETUP_EXCB |
> -                       AD7746_EXCSETUP_EXCLVL(3);

This logic is problematic now.
Because no matter what you're setting in the DT, it always gets
overridden here because there is no platform data.

Maybe a better idea is to do something like:
if (!pdata)
     regval = AD7746_EXCSETUP_EXCLVL(3);

but this should be placed somewhere around [1]


> +               regval = AD7746_EXCSETUP_EXCLVL(3);
>         }
>
>         ret = i2c_smbus_write_byte_data(chip->client,
> diff --git a/drivers/staging/iio/cdc/ad7746.h b/drivers/staging/iio/cdc/ad7746.h
> index 8bdbd732dbbd..6cae4ecf779e 100644
> --- a/drivers/staging/iio/cdc/ad7746.h
> +++ b/drivers/staging/iio/cdc/ad7746.h
> @@ -19,10 +19,6 @@
>
>  struct ad7746_platform_data {
>         unsigned char exclvl;   /*Excitation Voltage Level */
> -       bool exca_en;           /* enables EXCA pin as the excitation output */
> -       bool exca_inv_en;       /* enables /EXCA pin as the excitation output */
> -       bool excb_en;           /* enables EXCB pin as the excitation output */
> -       bool excb_inv_en;       /* enables /EXCB pin as the excitation output */
>  };
>
>  #endif /* IIO_CDC_AD7746_H_ */
> --
> 2.31.1
>