linux-kernel - Re: [PATCH v2 2/2] iio: potentiometer: Add driver support for AD5110

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Date:   Tue, 10 Aug 2021 15:49:52 +0300
From:   Andy Shevchenko <andy.shevchenko@...il.com>
To:     Mugilraj Dhavachelvan <dmugil2000@...il.com>
Cc:     "Bogdan, Dragos" <Dragos.Bogdan@...log.com>,
        Darius <Darius.Berghe@...log.com>,
        Rob Herring <robh+dt@...nel.org>,
        Jonathan Cameron <jic23@...nel.org>,
        Lars-Peter Clausen <lars@...afoo.de>,
        Michael Hennerich <Michael.Hennerich@...log.com>,
        Guenter Roeck <linux@...ck-us.net>,
        Chris Packham <chris.packham@...iedtelesis.co.nz>,
        Slawomir Stepien <sst@...zta.fm>,
        Krzysztof Kozlowski <krzk@...nel.org>,
        Alexandre Belloni <alexandre.belloni@...tlin.com>,
        Alexandru Ardelean <alexandru.ardelean@...log.com>,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-iio@...r.kernel.org
Subject: Re: [PATCH v2 2/2] iio: potentiometer: Add driver support for AD5110

On Mon, Aug 9, 2021 at 10:59 AM Mugilraj Dhavachelvan
<dmugil2000@...il.com> wrote:
>
> The AD5110/AD5112/AD5114 provide a nonvolatile solution
> for 128-/64-/32-position adjustment applications, offering
> guaranteed low resistor tolerance errors of ±8% and up to
> ±6 mA current density.

...

> +/*
> + * Analog Devices AD5110 digital potentiometer driver
> + *
> + * Copyright (C) 2021 Mugilraj Dhavachelvan <dmugil2000@...il.com>
> + *
> + * Datasheet: https://www.analog.com/media/en/technical-documentation/data-sheets/AD5110_5112_5114.pdf

> + *

Redundant blank line.

> + */

...

> +#define WIPER_RESISTANCE       70

Missed prefix?

...

> +static const struct iio_chan_spec ad5110_channels[] = {
> +       {
> +               .type = IIO_RESISTANCE,
> +               .output = 1,
> +               .info_mask_separate = BIT(IIO_CHAN_INFO_RAW) | BIT(IIO_CHAN_INFO_OFFSET) |
> +                                       BIT(IIO_CHAN_INFO_SCALE) | BIT(IIO_CHAN_INFO_ENABLE),
> +       }

+ comma.

> +};

...

> +       ret = i2c_master_send_dmasafe(data->client, data->buf, sizeof(data->buf));
> +       if (ret != sizeof(data->buf)) {

> +               ret = -EIO;

Shadowed error code when ret < 0.

> +               goto error;
> +       }

...

> +       ret = i2c_master_send_dmasafe(data->client, data->buf, sizeof(data->buf));
> +       if (ret != sizeof(data->buf))
> +               ret = -EIO;

Ditto.

> +       mutex_unlock(&data->lock);
> +
> +       return ret < 0 ? ret : 0;
> +}

...

> +       data->tol = data->cfg->kohms * (val & GENMASK(6, 0)) * 10 / 8;
> +       if (!(val & BIT(7)))
> +               data->tol *= -1;

Shouldn't you simple use corresponding sign_extend*()?

...

> +       ret = ad5110_write(data, AD5110_EEPROM_WR, 0);
> +       if (ret) {
> +               dev_err(&data->client->dev, "RDAC to EEPROM write failed\n");
> +               return ret;
> +       }


> +       msleep(20);

Each long sleeps like this must be explained.

...

> +static IIO_DEVICE_ATTR(store_eeprom, 0644,
> +                      ad5110_eeprom_read,
> +                      ad5110_eeprom_write, 0);

IIO_DEVICE_ATTR_RW() ?

...

> +static struct attribute *ad5110_attributes[] = {
> +       &iio_dev_attr_store_eeprom.dev_attr.attr,
> +       NULL,

No comma for a terminator line.

> +};

...

> +       data->cfg = device_get_match_data(dev);

> +       if (!data->cfg)
> +               data->cfg = &ad5110_cfg[i2c_match_id(ad5110_id, client)->driver_data];

Not sure this is not a dead code since you are using ->probe_new().

...

> +static struct i2c_driver ad5110_driver = {
> +       .driver = {
> +               .name   = "ad5110",
> +               .of_match_table = ad5110_of_match,
> +       },
> +       .probe_new      = ad5110_probe,
> +       .id_table       = ad5110_id,
> +};

> +

Redundant blank line.

> +module_i2c_driver(ad5110_driver);

-- 
With Best Regards,
Andy Shevchenko