Re: [Qemu-devel] [PATCH v2 26/74] pc: acpi: memhp: move MHPD._STA method into SSDT

[Michael S. Tsirkin]

On Mon, Dec 21, 2015 at 06:31:40PM +0100, Igor Mammedov wrote:
> On Sun, 20 Dec 2015 15:41:22 +0200
> "Michael S. Tsirkin" <address@hidden> wrote:
> 
> > On Wed, Dec 16, 2015 at 03:47:35PM +0100, Igor Mammedov wrote:
> [...]
> > > +        method = aml_method("_STA", 0, AML_NOTSERIALIZED);
> > > +        ifctx = aml_if(aml_equal(a_slots_nr, a_zero));
> > > +        {
> > > +             aml_append(ifctx, aml_return(a_zero));
> > > +        }
> > > +        aml_append(method, ifctx);
> > > +        /* present, functioning, decoding, not shown in UI */
> > > +        aml_append(method, aml_return(aml_int(0xB)));
> > > +        aml_append(ctrl_dev, method);
> > 
> > 
> > Simple unserialized methods that return value depending on input
> > being zero seem very common.  How about a helper for this case?
> > 
> > E.g.
> > 
> > aml_method_if_then_else(slots_nr, aml_int(0xB), aml_int(0));
> I've looked through all _STA methods that exist in DSDT
> and though this method for mem hotplug doesn't belong to common pattern,
> I could use you suggestion for 4 ISA devices.
> 
> Or perhaps I can save 2-3 LOC by making common
>   build_if_else(cond, truectx, false_ctx);
> I'll try both but it looks like build_if_else() will be more useful.

Yes but the issue is it makes code look weird since
you need to prepare the context ahead of the time.

> And after this series is applied there is a plenty to optimize,
> for example most of these _STA methods will be gone or replaced
> by simple _STA = FOO expression.

OK.

> 
> > 
> > >      }
> > >      aml_append(pci_scope, ctrl_dev);
> > >      aml_append(ctx, pci_scope);
> > > diff --git a/hw/i386/acpi-dsdt-mem-hotplug.dsl 
> > > b/hw/i386/acpi-dsdt-mem-hotplug.dsl
> > > index c2bb6a1..b4eacc9 100644
> > > --- a/hw/i386/acpi-dsdt-mem-hotplug.dsl
> > > +++ b/hw/i386/acpi-dsdt-mem-hotplug.dsl
> > > @@ -35,14 +35,6 @@
> > >              External(MEMORY_SLOT_OST_EVENT, FieldUnitObj) // _OST event 
> > > code, write only
> > >              External(MEMORY_SLOT_OST_STATUS, FieldUnitObj) // _OST 
> > > status code, write only
> > >  
> > > -            Method(_STA, 0) {
> > > -                If (LEqual(MEMORY_SLOTS_NUMBER, Zero)) {
> > > -                    Return(0x0)
> > > -                }
> > > -                /* present, functioning, decoding, not shown in UI */
> > > -                Return(0xB)
> > > -            }
> > > -
> > >              Mutex (MEMORY_SLOT_LOCK, 0)
> > >  
> > >              Method(MEMORY_SLOT_SCAN_METHOD, 0) {
> > > -- 
> > > 1.8.3.1