linux-kernel - Re: [PATCH v5 5/5] counter: 104-quad-8: Add IRQ support for the ACCES 104-QUAD-8

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Date:   Sun, 18 Oct 2020 10:50:25 -0400
From:   William Breathitt Gray <vilhelm.gray@...il.com>
To:     David Lechner <david@...hnology.com>
Cc:     jic23@...nel.org, kamel.bouhara@...tlin.com, gwendal@...omium.org,
        alexandre.belloni@...tlin.com, linux-iio@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        linux-stm32@...md-mailman.stormreply.com,
        linux-arm-kernel@...ts.infradead.org, syednwaris@...il.com,
        patrick.havelange@...ensium.com, fabrice.gasnier@...com,
        mcoquelin.stm32@...il.com, alexandre.torgue@...com
Subject: Re: [PATCH v5 5/5] counter: 104-quad-8: Add IRQ support for the
 ACCES 104-QUAD-8

On Tue, Oct 13, 2020 at 07:13:32PM -0500, David Lechner wrote:
> On 9/26/20 9:18 PM, William Breathitt Gray wrote:
> > +static irqreturn_t quad8_irq_handler(int irq, void *quad8iio)
> > +{
> > +	struct quad8_iio *const priv = quad8iio;
> > +	const unsigned long base = priv->base;
> > +	unsigned long irq_status;
> > +	unsigned long channel;
> > +	u8 event;
> > +	int err;
> > +
> > +	irq_status = inb(base + QUAD8_REG_INTERRUPT_STATUS);
> > +	if (!irq_status)
> > +		return IRQ_NONE;
> > +
> > +	for_each_set_bit(channel, &irq_status, QUAD8_NUM_COUNTERS) {
> > +		switch (priv->irq_trigger[channel]) {
> > +		case 0:
> > +			event = COUNTER_EVENT_OVERFLOW;
> > +				break;
> > +		case 1:
> > +			event = COUNTER_EVENT_THRESHOLD;
> > +				break;
> > +		case 2:
> > +			event = COUNTER_EVENT_OVERFLOW_UNDERFLOW;
> > +				break;
> > +		case 3:
> > +			event = COUNTER_EVENT_INDEX;
> > +				break;
> > +		default:
> > +			/* We should never reach here */
> > +			return -EINVAL;
> 
> This is not a valid return value for an IRQ handler. Maybe WARN_ONCE instead?

Ack.

> > +		}
> > +		err = counter_push_event(&priv->counter, event, channel);
> > +		if (err)
> > +			return err;
> 
> Same here. Otherwise, I think we could end up with interrupts in an endless
> loop since the interrupt would never be cleared.

Good point, I'll change this and the one above.

William Breathitt Gray

> > +	}
> > +
> > +	/* Clear pending interrupts on device */
> > +	outb(QUAD8_CHAN_OP_ENABLE_INTERRUPT_FUNC, base + QUAD8_REG_CHAN_OP);
> > +
> > +	return IRQ_HANDLED;
> > +}
> > +
> 

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