On Mon, Feb 03, 2025 at 02:36:58PM +0200, Mika Westerberg wrote:
> On Mon, Feb 03, 2025 at 05:54:18PM +0530, Sunil V L wrote:
> > On Mon, Feb 03, 2025 at 12:58:40PM +0200, Mika Westerberg wrote:
> > > On Mon, Feb 03, 2025 at 11:43:26AM +0200, Andy Shevchenko wrote:
> > > > On Mon, Feb 03, 2025 at 02:19:01PM +0530, Anup Patel wrote:
> > > > > From: Sunil V L <sunilvl@xxxxxxxxxxxxxxxx>
> > > > >
> > > > > fwnode_get_reference_args() which is common for both DT and ACPI passes
> > > > > a property name like #mbox-cells which needs to be fetched from the
> > > > > reference node to determine the number of arguments needed for the
> > > > > property. However, the ACPI version of this function doesn't support
> > > > > this and simply ignores the parameter passed from the wrapper function.
> > > > > Add support for dynamically finding number of arguments by reading the
> > > > > nargs property value. Update the callers to pass extra parameter.
> > > >
> > > > I don't like this (implementation).
> > >
> > > Agree.
> > >
> > > > It seems that we basically have two parameters which values are duplicating
> > > > each other. This is error prone API and confusing in the cases when both are
> > > > defined. If you want property, add a new API that takes const char *nargs
> > > > and relies on the property be present.
> > >
> > > Also this is not really needed for ACPI case because it has types so it can
> > > distinguish references from integer. Having separate property for this just
> > > makes things more complex than they need to be IMHO.
> >
> > Thanks! Andy and Mika for your kind feedback. I agree that having both
> > property name and nargs is confusing and also ACPI would not need
> > nargs_prop. In fact, I think ACPI doesn't need even nargs integer value
> > as well from the caller since all integers after the reference are
> > counted as arguments. However, the issue is acpi_get_ref_args() assumes
> > that caller passes valid num_args. But typically the common
> > fwnode_property_get_reference_args() doesn't usually pass both valid
> > values. So, should fwnode_property_get_reference_args() pass both
> > nargs_prop (for DT) and nargs (for ACPI). Or do you mean it is better to
> > remove the check for num_args in the loop inside acpi_get_ref_args()
> > function?
>
> Can you show an example of a case you are trying to solve with this? So far
> we have been able to go with the current implementation so why this is
> needed now?
Basically one can call fwnode_property_get_reference_args()
irrespective of DT/ACPI. The case we are trying is like below.
if (fwnode_property_get_reference_args(dev->fwnode, "mboxes",
"#mbox-cells", 0, index, &fwspec)) {
...
}
As you can see this works for DT since OF interface handles
"#mbox-cells". But since nargs is passed as 0, it won't work for ACPI
due to the reason I mentioned earlier.
Mandating to pass both "#mbox-cell" and valid nargs count looks
redundant to me.
Thanks,
Sunil
