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

[Paul Cercueil]

Hi Andy,

Le mar. 19 mai 2020 à 23:43, Andy Shevchenko 
<andy.shevchenko@xxxxxxxxx> a écrit :
> On Sun, May 17, 2020 at 10:49 PM Artur Rojek <contact@xxxxxxxxxxxxxx> 
> 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()?

I'll answer this one:

The sign can be uppercase to specify that the value is sign-extended in 
all the storage bits.

-Paul

> >  +
> >  +               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