linux-kernel - Re: [RESEND PATCH v5 5/5] input: joystick: Add ADC attached joystick driver.

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Message-Id: <UFBY8Q.ES4D59V22INC1@crapouillou.net>
Date:   Fri, 17 Apr 2020 23:23:54 +0200
From:   Paul Cercueil <paul@...pouillou.net>
To:     Andy Shevchenko <andy.shevchenko@...il.com>
Cc:     Artur Rojek <contact@...ur-rojek.eu>,
        Dmitry Torokhov <dmitry.torokhov@...il.com>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Jonathan Cameron <jic23@...nel.org>,
        Heiko Stuebner <heiko@...ech.de>,
        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: [RESEND PATCH v5 5/5] input: joystick: Add ADC attached joystick
 driver.

Hi Andy,

Le sam. 18 avril 2020 à 0:10, Andy Shevchenko 
<andy.shevchenko@...il.com> a écrit :
> On Fri, Apr 17, 2020 at 11:21 PM Artur Rojek <contact@...ur-rojek.eu> 
> wrote:
>> 
>>  Add a driver for joystick devices connected to ADC controllers
>>  supporting the Industrial I/O subsystem.
> 
> ...
> 
>>  +#include <linux/of.h>
> 
> Do you really need this? (See below as well)
> 
> ...
> 
>>  +               sign = 
>> (tolower(joy->chans[i].channel->scan_type.sign) == 's');
> 
> Too many parentheses. But here it's up to you,
> 
> ...
> 
>>  +               case 2:
> 
>>  +                       val = ((const u16 *)data)[i];
> 
> Can't you do this in each branch below?
> 
>>  +                       if (endianness == IIO_BE)
>>  +                               val = be16_to_cpu(val);
>>  +                       else if (endianness == IIO_LE)
>>  +                               val = le16_to_cpu(val);
>>  +                       break;
> 
> ...
> 
>>  +       device_for_each_child_node(dev, child) {
>>  +               ret = fwnode_property_read_u32(child, "reg", &i);
>>  +               if (ret || i >= num_axes) {
>>  +                       dev_err(dev, "reg invalid or missing");
>>  +                       goto err;
>>  +               }
>>  +
>>  +               if (fwnode_property_read_u32(child, "linux,code",
>>  +                                            &axes[i].code)) {
>>  +                       dev_err(dev, "linux,code invalid or 
>> missing");
>>  +                       goto err;
>>  +               }
>>  +
>>  +               if (fwnode_property_read_u32_array(child, 
>> "abs-range",
>>  +                                                  axes[i].range, 
>> 2)) {
>>  +                       dev_err(dev, "abs-range invalid or 
>> missing");
>>  +                       goto err;
>>  +               }
> 
>>  +       }
>>  +
>>  +       joy->axes = axes;
>>  +
>>  +       return 0;
>>  +
>>  +err:
>>  +       fwnode_handle_put(child);
> 
>>  +       return -EINVAL;
> 
> Can we avoid shadowing the actual error code?
> 
> ...
> 
>>  +       bits = joy->chans[0].channel->scan_type.storagebits;
> 
>>  +       if (!bits || (bits >> 3) > 2) {
> 
> Wouldn't be clear to use simple 'bits > 16'?
> 
>>  +               dev_err(dev, "Unsupported channel storage size");
>>  +               return -EINVAL;
>>  +       }
> 
> ...
> 
>>  +static const struct of_device_id adc_joystick_of_match[] = {
>>  +       { .compatible = "adc-joystick", },
>>  +       { },
>>  +};
>>  +MODULE_DEVICE_TABLE(of, adc_joystick_of_match);
>>  +
>>  +static struct platform_driver adc_joystick_driver = {
>>  +       .driver = {
>>  +               .name = "adc-joystick",
> 
>>  +               .of_match_table = 
>> of_match_ptr(adc_joystick_of_match),
> 
> Drop this a bit harmful of_match_ptr() macro. It should go with ugly
> #ifdeffery. Here you simple introduced a compiler warning.

I assume you mean #ifdef around the of_device_id + module table macro?

> On top of that, you are using device property API, OF use in this case
> is contradictory (at lest to some extend).

I don't see why. The fact that the driver can work when probed from 
platform code, doesn't mean that it shouldn't have a table to probe 
from devicetree.

-Paul

> 
>>  +       },
>>  +       .probe = adc_joystick_probe,
>>  +};
> 
> --
> With Best Regards,
> Andy Shevchenko