From: "Suthikulpanit, Suravee" <Suravee.Suthikulpanit@amd.com>
To: "Rafael J. Wysocki" <rjw@rjwysocki.net>
CC: "Zheng, Lv" <lv.zheng@intel.com>,
        "mika.westerberg@linux.intel.com" <mika.westerberg@linux.intel.com>,
        "Moore, Robert" <robert.moore@intel.com>,
        "hanjun.guo@linaro.org" <hanjun.guo@linaro.org>,
        "lenb@kernel.org" <lenb@kernel.org>,
        "hdegoede@redhat.com" <hdegoede@redhat.com>,
        "tj@kernel.org" <tj@kernel.org>,
        "mjg59@srcf.ucam.org" <mjg59@srcf.ucam.org>,
        "gregkh@linuxfoundation.org" <gregkh@linuxfoundation.org>,
        "al.stone@linaro.org" <al.stone@linaro.org>,
        "graeme.gregory@linaro.org" <graeme.gregory@linaro.org>,
        "Duran, Leo" <leo.duran@amd.com>,
        "linux-ide@vger.kernel.org" <linux-ide@vger.kernel.org>,
        "linux-acpi@vger.kernel.org" <linux-acpi@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "linaro-acpi@lists.linaro.org" <linaro-acpi@lists.linaro.org>
Subject: Re: [V8 PATCH 1/3] ACPICA: Add ACPI _CLS processing
Thread-Topic: [V8 PATCH 1/3] ACPICA: Add ACPI _CLS processing
Thread-Index: AQHQazReni7SfDxa00Gyt8V9xTy7lJ1QzR4AgAvxV4CAAK1ZgIACkmaA
Date: Sun, 26 Apr 2015 22:45:29 +0000
Message-ID: <D162D21D.19BCD%suravee.suthikulpanit@amd.com>
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On 4/24/15, 21:28, "Rafael J. Wysocki" <rjw@rjwysocki.net> wrote:

>On Friday, April 24, 2015 04:08:31 PM Suravee Suthikulpanit wrote:
>> On 4/16/15 20:45, Zheng, Lv wrote:
>> > Before back porting this to ACPICA, let me ask one simple question.
>> > According to the spec, the _CLS is optional and PCI specific.
>> > So why should we implement it in ACPICA core not OSPM specific
>>modules?
>> > If this need to be implemented in ACPICA, then what about the
>>following device identification objects?
>> > _DDN, _HRV, _MLS, _PLD, _STR, _SUN
>> >
>> > Thanks and best regards
>> > -Lv
>> 
>> Hi,
>> 
>> Sorry for late reply. As for the justification for introducing the _CLS
>> support in the ACPICA, this is mainly because ACPI does not currently
>> define _CID for certain device classes, which used to mostly be PCI
>> devices. Instead, ACPI spec mentioned that _CLS can be used for loading
>> generic drivers on hardware that is compatible with PCI-defined device
>> classes, but that is not implemented on the PCI bus (and is therefore
>> enumerated by ACPI.)
>
>I think it would be good to point to the particular part of the spec
>making that provision.  In what section is that mentioned, exactly?

Here is the copied from section 6.1.3 _CLS (Class Code) from ACPI 5.1 spec:
"This object is used to supply OSPM with the PCI-defined class, subclass
and programming interface for a device. This object is optional but may be
useful for generic drivers written for PCI devices that move off of PCI
and are enumerated by ACPI.?

Otherwise, if the community think it?s better to not putting the _CLS the
_CLS parsing code in ACPICA since, I can try looking into pulling the code
out of ACPICA. I also noticed a little issue in the patch series where the
ACPI_VALID_CLS is used in the patch 1 but defined in patch 2. I can send
out v9 with the fix once we agree on the _CLS parsing.

Thanks,

Suravee

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