On Sun, May 17, 2020 at 10:49 PM Artur Rojek [off-list ref] 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