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

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Message-ID: <20210811054558.GA3826@mugil-Nitro-AN515-52>
Date:   Wed, 11 Aug 2021 11:15:58 +0530
From:   Mugilraj Dhavachelvan <dmugil2000@...il.com>
To:     Andy Shevchenko <andy.shevchenko@...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>,
        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 Tue, Aug 10, 2021 at 03:49:52PM +0300, Andy Shevchenko wrote:
> 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.
> 
fixed in v3
> > + */
> 
> ...
> 
> > +#define WIPER_RESISTANCE       70
> 
> Missed prefix?
> 
fixed in v3
> ...
> 
> > +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.
> 
fixed in v3
> > +};
> 
> ...
> 
> > +       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.
> 
fixed in v3
> > +               goto error;
> > +       }
> 
> ...
> 
> > +       ret = i2c_master_send_dmasafe(data->client, data->buf, sizeof(data->buf));
> > +       if (ret != sizeof(data->buf))
> > +               ret = -EIO;
> 
> Ditto.
> 
fixed in v3
> > +       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*()?
> 
I'm not able see any sign_extend for 16 bit. Is there any other way?
> ...
> 
> > +       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.
> 
fixed in v3
> ...
> 
> > +static IIO_DEVICE_ATTR(store_eeprom, 0644,
> > +                      ad5110_eeprom_read,
> > +                      ad5110_eeprom_write, 0);
> 
> IIO_DEVICE_ATTR_RW() ?
> 
fixed in v3
> ...
> 
> > +static struct attribute *ad5110_attributes[] = {
> > +       &iio_dev_attr_store_eeprom.dev_attr.attr,
> > +       NULL,
> 
> No comma for a terminator line.
> 
fixed in v3
> > +};
> 
> ...
> 
> > +       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().
> 
Even I'm suspecting that and also removing id_table. But I'm not sure of
it so just left as it is.
> ...
> 
> > +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
fixed in v3.
> 
> > +module_i2c_driver(ad5110_driver);
> 
Thanks for the feedback :)
> -- 
> With Best Regards,
> Andy Shevchenko