[v9,1/2] dt-bindings: input: Add docs for ADC driven joystick.

Add documentation for the adc-joystick driver, used to provide support
for joysticks connected over ADC.

Signed-off-by: Artur Rojek <contact@artur-rojek.eu>
Tested-by: Paul Cercueil <paul@crapouillou.net>
Reviewed-by: Rob Herring <robh@kernel.org>
---

Changes:
    v6-v9: no change

 .../bindings/input/adc-joystick.yaml          | 121 ++++++++++++++++++
 1 file changed, 121 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/input/adc-joystick.yaml

On Sat, Sep 5, 2020 at 7:34 PM Artur Rojek <contact@artur-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, 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?
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?

> +               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.

...

> +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;
> +               }
> +       }

On Sun, Sep 06, 2020 at 02:09:28PM +0200, Artur Rojek wrote:
> 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@artur-rojek.eu>
> > wrote:
> > 
> > > +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?

If there are lifetime issues they would be in input core, not individual
driver. But input core ensures that it calls close (if open was called
earlier) before doing input device teardown.

> > 
> > ...
> > 
> > > +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?

/* Math result not representable */

? Seems not any better than -EINVAL.

Thanks.