Re: [PATCH RFC 02/11] ACPI: Introduce irq_get() for static fwnodes

[Andy Shevchenko]

On Fri, Sep 25, 2026 at 12:30:07PM +0200, Lorenzo Pieralisi wrote:
> On Fri, Sep 25, 2026 at 12:49:54PM +0300, Andy Shevchenko wrote:
> > On Fri, Sep 25, 2026 at 09:48:01AM +0200, Lorenzo Pieralisi wrote:

...

> > > +static int acpi_static_fwnode_read_u32_prop_index(const struct fwnode_handle *fwnode,
> > > +						  const char *propname,
> > > +						  unsigned int index, u32 *value)
> > > +{
> > > +	u32 *values;
> > > +	int ret, count;
> > > +
> > > +	count = fwnode_property_count_u32(fwnode, propname);
> > > +	if (count < 0)
> > > +		return count;
> > > +
> > > +	if (index >= count)
> > > +		return -ENOENT;
> > > +
> > > +	values = kcalloc(count, sizeof(*values), GFP_KERNEL);
> > > +	if (!values)
> > > +		return -ENOMEM;
> > > +
> > > +	ret = fwnode_property_read_u32_array(fwnode, propname, values, count);
> > > +	if (!ret)
> > > +		*value = values[index];
> > 
> > Use standard pattern, id est
> > 
> > 	if (ret)
> > 		...
> > 
> > > +	kfree(values);
> > 
> > You want to use __free()
> > 
> > > +	return ret;
> > > +}
> > 
> > I believe the whole approach is suboptimal, if you wish get indexed value (but why?)
> 
> Why what (that's what the irq_get() interface requires ?) I agree it is
> suboptimal - the whole point of the series is an RFC on using properties
> to store GSI number/flags, then how to read them we will optimize it
> when/if we agree that's the approach to be taken.

Why to have indexed APIs. The callers usually do not want a single item from an
array, they want all of them or a big pile (exception is the array of strings,
but we have matching functions for that).

As per approach, this patch is against device property and I don't think we are
going to agree on the approach taken in *this* patch.

> > it needs to be retrieved as that in the guts of ACPI. Allocating memory for the whole
> > array to retrieve a single element is simply wrong.

...

> > > +#define ACPI_IRQ_PROP_GSI		"linux,acpi-gsi"
> > > +#define ACPI_IRQ_PROP_GSI_TRIGGER	"linux,acpi-gsi-trigger"
> > > +#define ACPI_IRQ_PROP_GSI_POLARITY	"linux,acpi-gsi-polarity"
> > 
> > Oh... This sounds like a big ugly hack.
> 
> That does not help much I am afraid.
> 
> What's a ugly hack ? Property names ? Using properties for this purpose ?

Yes, properties started with "linux," for some core functionality.
Yes, using properties for this also doesn't sound right. I think the problem
here is in the table specifications or somewhere that deep. That's why we
ended up in this series.

> Again, it is an RFC for this specific reason and I mentioned that in the
> cover letter, thank you for your inputs.

And here we have a discussion started :-)

P.S. Looks like I was too quick to jump into this thread. I will wait for
others to share their view on all this.

-- 
With Best Regards,
Andy Shevchenko