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

From: Xiao Guangrong <guangrong.xiao@linux.intel.com>
To: Igor Mammedov <imammedo@redhat.com>
Cc: pbonzini@redhat.com, gleb@kernel.org, mtosatti@redhat.com,
	stefanha@redhat.com, mst@redhat.com, rth@twiddle.net,
	ehabkost@redhat.com, dan.j.williams@intel.com,
	kvm@vger.kernel.org, qemu-devel@nongnu.org
Subject: Re: [PATCH v2 04/11] acpi: add aml_concatenate()
Date: Mon, 15 Feb 2016 18:32:45 +0800	[thread overview]
Message-ID: <56C1A94D.2060500@linux.intel.com> (raw)
In-Reply-To: <20160215100243.703e00da@nial.brq.redhat.com>

On 02/15/2016 05:02 PM, Igor Mammedov wrote:
> On Sun, 14 Feb 2016 13:55:24 +0800
> Xiao Guangrong <guangrong.xiao@linux.intel.com> 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 <guangrong.xiao@linux.intel.com> wrote:
>>>>
>>>>> It will be used by nvdimm acpi
>>>>>
>>>>> Signed-off-by: Xiao Guangrong <guangrong.xiao@linux.intel.com>
>>>>> ---
>>>>>    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.
>

Yes, you are right, i re-checked the spec and it said that "Source2 is
concatenated to Source1 and the result data is optionally stored into Result" so that
@target can be eliminated.