Re: [RFC PATCH] genirq: implement read_irq_line for interrupt lines

[Abhijeet Dharmapurikar]

David Daney wrote:
> On 04/15/2011 11:42 AM, Abhijeet Dharmapurikar wrote:
> [...]
> > +/**
> > + *    irq_read_line - read the value on an irq line
> > + *    @irq: Interrupt number representing a hardware line
> > + *
> > + *    This function may be called from IRQ context only when
> > + *    desc->chip->bus_lock and desc->chip->bus_sync_unlock are NULL !
>
> What does it return?  I can see that -EINVAL is returned if it isn't 
> applicable to this irq.  But what if chip->irq_read_line is implemented?

It returns the logical state of that line (0 when it is low or 1 when it 
is high). Will add the return type in the comment.

> > + */
> > +int irq_read_line(unsigned int irq)
> > +{
> > +    struct irq_desc *desc = irq_to_desc(irq);
> > +    unsigned long flags;
> > +    int val;
> > +
> > +    if (!desc || !desc->irq_data.chip->irq_read_line)
> > +        return -EINVAL;

It returns -EINVAL is irq_read_line is not implemented.

> > +
> > +    chip_bus_lock(desc);
> > +    raw_spin_lock_irqsave(&desc->lock, flags);



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