Re: [PATCH v13 09/12] ACPI: x86: s2idle: Add a function to get constraints for a device

[Mario Limonciello]

On 8/18/2023 05:47, Andy Shevchenko wrote:
> On Fri, Aug 18, 2023 at 10:31:03AM +0200, Rafael J. Wysocki wrote:
> > On Fri, Aug 18, 2023 at 7:15 AM Mario Limonciello
> > <mario.limonciello@xxxxxxx> wrote:
>
> ...
>
> > > +int acpi_get_lps0_constraint(struct device *dev)
> >
> > I think that some overhead would be reduced below if this were taking
> > a struct acpi_device pointer as the argument.
>
> Hmm... Either you need a pointer to handle, which involves pointer arithmetics
> or something else. I would believe if you tell that ACPI handle should be passed,
> but current suggestion is not obvious to me how it may help.

To Rafael's point about overhead there are potentially "less" calls into 
acpi_get_lps0_constraint if it's a 'struct acpi_device' pointer because 
it won't be called by caller for any devices that don't have an ACPI 
companion.

> > > +{
> > > +       struct lpi_constraints *entry;
> > > +
> > > +       for_each_lpi_constraint(entry) {
> > > +               if (!device_match_acpi_handle(dev, entry->handle))
>
> Here we retrieve handle...
>
> > > +                       continue;
> > > +               acpi_handle_debug(entry->handle,
> > > +                                 "ACPI device constraint: %d\n", entry->min_dstate);
> > > +               return entry->min_dstate;
> > > +       }
>
> > > +       dev_dbg(dev, "No ACPI device constraint specified\n");
>
> ...and here we are using dev directly (otherwise acpi_handle_dbg() should be used).

I'll just move the debugging statements into the caller of 
acpi_get_lps0_constraint().

> > > +       return -ENODEV;
> >
> > ACPI_STATE_UNKNOWN?

Much better, thanks.

> > > +}