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SubjectRe: [PATCH v11 18/33] counter: Return error code on invalid modes
On Wed, Jun 09, 2021 at 04:47:31PM +0100, Jonathan Cameron wrote:
> On Wed, 9 Jun 2021 10:31:21 +0900
> William Breathitt Gray <vilhelm.gray@gmail.com> wrote:
> > diff --git a/drivers/counter/stm32-lptimer-cnt.c b/drivers/counter/stm32-lptimer-cnt.c
> > index c19d998df5ba..78f383b77bd2 100644
> > --- a/drivers/counter/stm32-lptimer-cnt.c
> > +++ b/drivers/counter/stm32-lptimer-cnt.c
> > @@ -206,9 +206,10 @@ static int stm32_lptim_cnt_function_set(struct counter_device *counter,
> > priv->quadrature_mode = 1;
> > priv->polarity = STM32_LPTIM_SYNAPSE_ACTION_BOTH_EDGES;
> > return 0;
> > + default:
> > + /* should never reach this path */
> > + return -EINVAL;
>
> In this particular case we are already exhaustive. So we should have neither default
> nor ideally the return below.
>
> If we have a local variable of the relevant enum type, then I think the compiler
> should be able to tell this is exhaustive and usefully it will then issue
> a warning should the enum gain more entries in future.

I tried using a local variable of type enum stm32_lptim_cnt_function,
but unfortunately the compiler is not able to tell this is exhaustive --
I think it's because 'function' is of type enum counter_function which
can theoretically have a value outside enum stm32_lptim_cnt_function.

>
> > }
> > -
> > - return -EINVAL;
> > }
> >
> > static ssize_t stm32_lptim_cnt_enable_read(struct counter_device *counter,
> > @@ -326,9 +327,10 @@ static int stm32_lptim_cnt_action_get(struct counter_device *counter,
> > case STM32_LPTIM_ENCODER_BOTH_EDGE:
> > *action = priv->polarity;
> > return 0;
> > + default:
>
> Same in this path.
>
> > + /* should never reach this path */
> > + return -EINVAL;
> > }
> > -
> > - return -EINVAL;
> > }
> >
> > static int stm32_lptim_cnt_action_set(struct counter_device *counter,
> > diff --git a/drivers/counter/ti-eqep.c b/drivers/counter/ti-eqep.c
> > index 65df9ef5b5bc..878725c2f010 100644
> > --- a/drivers/counter/ti-eqep.c
> > +++ b/drivers/counter/ti-eqep.c
> > @@ -157,44 +157,39 @@ static int ti_eqep_action_get(struct counter_device *counter,
> > * QEPA and QEPB trigger QCLK.
> > */
> > *action = TI_EQEP_SYNAPSE_ACTION_BOTH_EDGES;
> > - break;
> > + return 0;
> > case TI_EQEP_COUNT_FUNC_DIR_COUNT:
> > /* In direction-count mode only rising edge of QEPA is counted
> > * and QEPB gives direction.
> > */
> > - switch (synapse->signal->id) {
> I'd rather see this as
>
> case TI_EQEP_SIGNAL_QEPA:
> caes TI_EQEP_SIGNAL_QEPB:
>
> To make it clear what the two cases are. Then we don't need the default
> assuming the type is right so the compiler should be able to see
> that we have been exhaustive.

I can refactor this back to a switch statement as you suggest, but we'll
need the default case for the same reason as mentioned above.

William Breathitt Gray

>
> > - case TI_EQEP_SIGNAL_QEPA:
> > - *action = TI_EQEP_SYNAPSE_ACTION_RISING_EDGE;
> > - break;
> > - default:
> > + if (synapse->signal->id == TI_EQEP_SIGNAL_QEPB)
> > *action = TI_EQEP_SYNAPSE_ACTION_NONE;
> > - break;
> > - }
> > - break;
> > + else
> > + *action = TI_EQEP_SYNAPSE_ACTION_RISING_EDGE;
> > + return 0;
> > case TI_EQEP_COUNT_FUNC_UP_COUNT:
> > case TI_EQEP_COUNT_FUNC_DOWN_COUNT:
> > /* In up/down-count modes only QEPA is counted and QEPB is not
> > * used.
> > */
> > - switch (synapse->signal->id) {
> > - case TI_EQEP_SIGNAL_QEPA:
> > - err = regmap_read(priv->regmap16, QDECCTL, &qdecctl);
> > - if (err)
> > - return err;
> > -
> > - if (qdecctl & QDECCTL_XCR)
> > - *action = TI_EQEP_SYNAPSE_ACTION_BOTH_EDGES;
> > - else
> > - *action = TI_EQEP_SYNAPSE_ACTION_RISING_EDGE;
> > - break;
> > - default:
> > + if (synapse->signal->id == TI_EQEP_SIGNAL_QEPB) {
> > *action = TI_EQEP_SYNAPSE_ACTION_NONE;
>
> Same as above
>
> > - break;
> > + return 0;
> > }
> > - break;
> > - }
> >
> > - return 0;
> > + err = regmap_read(priv->regmap16, QDECCTL, &qdecctl);
> > + if (err)
> > + return err;
> > +
> > + if (qdecctl & QDECCTL_XCR)
> > + *action = TI_EQEP_SYNAPSE_ACTION_BOTH_EDGES;
> > + else
> > + *action = TI_EQEP_SYNAPSE_ACTION_RISING_EDGE;
> > + return 0;
> > + default:
> > + /* should never reach this path */
> > + return -EINVAL;
> > + }
> > }
> >
> > static const struct counter_ops ti_eqep_counter_ops = {
>
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