Re: [Qemu-devel] [PATCH v2 04/11] acpi: add aml_concatenate()

[Igor Mammedov]

On Sun, 14 Feb 2016 13:55:24 +0800
Xiao Guangrong <address@hidden> wrote:

> On 02/14/2016 01:52 PM, Xiao Guangrong wrote:
> >
> >
> > On 02/08/2016 06:51 PM, Igor Mammedov wrote:  
> >> On Wed, 13 Jan 2016 02:50:03 +0800
> >> Xiao Guangrong <address@hidden> wrote:
> >>  
> >>> It will be used by nvdimm acpi
> >>>
> >>> Signed-off-by: Xiao Guangrong <address@hidden>
> >>> ---
> >>>   hw/acpi/aml-build.c         | 14 ++++++++++++++
> >>>   include/hw/acpi/aml-build.h |  1 +
> >>>   2 files changed, 15 insertions(+)
> >>>
> >>> diff --git a/hw/acpi/aml-build.c b/hw/acpi/aml-build.c
> >>> index 97c9efb..421dd84 100644
> >>> --- a/hw/acpi/aml-build.c
> >>> +++ b/hw/acpi/aml-build.c
> >>> @@ -1440,6 +1440,20 @@ Aml *aml_alias(const char *source_object, const 
> >>> char *alias_object)
> >>>       return var;
> >>>   }
> >>>
> >>> +/* ACPI 1.0b: 16.2.5.4 Type 2 Opcodes Encoding: DefConcat */
> >>> +Aml *aml_concatenate(Aml *source1, Aml *source2, Aml *target)
> >>> +{
> >>> +    Aml *var = aml_opcode(0x73 /* ConcatOp */);
> >>> +    aml_append(var, source1);
> >>> +    aml_append(var, source2);
> >>> +
> >>> +    if (target) {
> >>> +        aml_append(var, target);
> >>> +    }  
> >> target is not an optional, pls looks at aml_add and use
> >> helper to make patch correct and smaller
> >>  
> >
> > Indeed, i will change it to:
> >
> > /* ACPI 1.0b: 16.2.5.4 Type 2 Opcodes Encoding: DefConcat */
> > Aml *aml_concatenate(Aml *source1, Aml *source2, Aml *target)
> > {
> >      return  build_opcode_2arg_dst(0x73 /* ConcatOp */, arg1, arg2, dst);
> > }
> >  
> 
> And make a assert for @target to ensure it can not be NULL.
Don't do that, see build_opcode_2arg_dst(), target can be NULL
that allows to express implicit target like:

  aml_add(a, aml_add(b, c, NULL), NULL)

where one doesn't need an intermediate variable to store result.