Re: [PATCH v9 2/2] input: joystick: Add ADC attached joystick driver.

[Artur Rojek]

Hi Andy,

thanks for the review, replies inline.

On 2020-09-06 11:22, Andy Shevchenko wrote:
> On Sat, Sep 5, 2020 at 7:34 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, idx, i;
> > +       bool sign;
> > +
> > +       bytes = joy->chans[0].channel->scan_type.storagebits >> 3;
> > +
> > +       for (i = 0; i < joy->num_chans; ++i) {
> > +               idx = joy->chans[i].channel->scan_index;
> > +               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');
>
> Redundant parentheses.
>
> > +               switch (bytes) {
> > +               case 1:
> > +                       val = ((const u8 *)data)[idx];
> > +                       break;
> > +               case 2:
>
> > +                       if (endianness == IIO_BE)
> > +                               val = be16_to_cpu(((const __be16 
> > *)data)[idx]);
> > +                       else if (endianness == IIO_LE)
> > +                               val = le16_to_cpu(((const __le16 
> > *)data)[idx]);
> > +                       else /* IIO_CPU */
> > +                               val = ((const u16 *)data)[idx];
> > +                       break;
>
> Hmm... I don't like explicit castings to restricted types. On top of
> that is it guaranteed that pointer to data will be aligned?
The buffer comes from the IIO core, it is aligned to the sample size.
> As a solution for the first two I would recommend to use
> get_unaligned_be16() / get_unaligned_le16().
> The last one is an interesting case and if data can be unaligned needs
> to be fixed.
>
> > +               default:
> > +                       return -EINVAL;
> > +               }
> > +
> > +               val >>= joy->chans[i].channel->scan_type.shift;
> > +               if (sign)
> > +                       val = sign_extend32(val, msb);
> > +               else
>
> > +                       val &= GENMASK(msb, 0);
>
> It includes msb. Is it expected?
Yes, that's expected as `msb = joy->chans[i].channel->scan_type.realbits 
- 1`.
> > +               input_report_abs(joy->input, joy->axes[i].code, val);
> > +       }
> > +
> > +       input_sync(joy->input);
> > +
> > +       return 0;
> > +}
>
> ...
>
> > +static int adc_joystick_open(struct input_dev *dev)
>
> > +static void adc_joystick_close(struct input_dev *dev)
>
> Just wondering if this is protected against object lifetime cases.
Can you clarify that in more details?
> ...
>
> > +err:
>
> err_fwnode_put: ?
>
> > +       fwnode_handle_put(child);
> > +       return ret;
>
> ...
>
> > +       /* Count how many channels we got. NULL terminated. */
> > +       for (i = 0; joy->chans[i].indio_dev; ++i) {
> > +               bits = joy->chans[i].channel->scan_type.storagebits;
> > +               if (!bits || (bits > 16)) {
> > +                       dev_err(dev, "Unsupported channel storage 
> > size\n");
>
> > +                       return -EINVAL;
>
> -ERANGE?
>
> > +               }
> > +               if (bits != 
> > joy->chans[0].channel->scan_type.storagebits) {
> > +                       dev_err(dev, "Channels must have equal storage 
> > size\n");
> > +                       return -EINVAL;
> > +               }
> > +       }