linux-kernel - Re: [PATCH v7 7/7] input: joystick: Add ADC attached joystick driver.

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Date:   Tue, 19 May 2020 23:43:44 +0300
From:   Andy Shevchenko <andy.shevchenko@...il.com>
To:     Artur Rojek <contact@...ur-rojek.eu>
Cc:     Dmitry Torokhov <dmitry.torokhov@...il.com>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Jonathan Cameron <jic23@...nel.org>,
        Paul Cercueil <paul@...pouillou.net>,
        Heiko Stuebner <heiko@...ech.de>,
        Ezequiel Garcia <ezequiel@...guardiasur.com.ar>,
        linux-input <linux-input@...r.kernel.org>,
        devicetree <devicetree@...r.kernel.org>,
        linux-iio <linux-iio@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v7 7/7] input: joystick: Add ADC attached joystick driver.

On Sun, May 17, 2020 at 10:49 PM Artur Rojek <contact@...ur-rojek.eu> wrote:
>
> Add a driver for joystick devices connected to ADC controllers
> supporting the Industrial I/O subsystem.

...

> +static int adc_joystick_handle(const void *data, void *private)
> +{
> +       struct adc_joystick *joy = private;
> +       enum iio_endian endianness;
> +       int bytes, msb, val, i;
> +       bool sign;
> +
> +       bytes = joy->chans[0].channel->scan_type.storagebits >> 3;
> +
> +       for (i = 0; i < joy->num_chans; ++i) {
> +               endianness = joy->chans[i].channel->scan_type.endianness;
> +               msb = joy->chans[i].channel->scan_type.realbits - 1;

> +               sign = (tolower(joy->chans[i].channel->scan_type.sign) == 's');

Do we need tolower()?

> +
> +               switch (bytes) {
> +               case 1:
> +                       val = ((const u8 *)data)[i];
> +                       break;
> +               case 2:
> +                       if (endianness == IIO_BE)

> +                               val = be16_to_cpu(((const u16 *)data)[i]);

Yeah, you have to provide bitwise types to satisfy sparse.
Maybe using *_to_cpup() will cure this.

> +                       else if (endianness == IIO_LE)
> +                               val = le16_to_cpu(((const u16 *)data)[i]);
> +                       else /* IIO_CPU */
> +                               val = ((const u16 *)data)[i];
> +                       break;
> +               default:
> +                       return -EINVAL;
> +               }
> +
> +               val >>= joy->chans[i].channel->scan_type.shift;
> +               if (sign)
> +                       val = sign_extend32(val, msb);
> +               else
> +                       val &= GENMASK(msb, 0);
> +               input_report_abs(joy->input, joy->axes[i].code, val);
> +       }
> +
> +       input_sync(joy->input);
> +
> +       return 0;
> +}

...

> +       /* Count how many channels we got. NULL terminated. */
> +       while (joy->chans[joy->num_chans].indio_dev)
> +               joy->num_chans++;

I don't see how useful this is. Why not simple do below...

> +       bits = joy->chans[0].channel->scan_type.storagebits;
> +       if (!bits || (bits > 16)) {
> +               dev_err(dev, "Unsupported channel storage size");
> +               return -EINVAL;
> +       }
> +       for (i = 1; i < joy->num_chans; ++i)
> +               if (joy->chans[i].channel->scan_type.storagebits != bits) {
> +                       dev_err(dev, "Channels must have equal storage size");
> +                       return -EINVAL;
> +               }

...something like

  for (i = 0; joy->chans[i].indio_dev; i++) {
    bits = joy->chans[i].channel->scan_type.storagebits;
    if (bits ...) {
      ...error handling...
    }
    if (bits != joy->chans[0].channel->scan_type.storagebits) {
      ...second level of error handling...
    }
 }

...

> +static const struct of_device_id adc_joystick_of_match[] = {
> +       { .compatible = "adc-joystick", },

> +       { },

No need comma.

> +};

-- 
With Best Regards,
Andy Shevchenko