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Message-ID: <553AB0CF.1010904@amd.com>
Date: Fri, 24 Apr 2015 16:08:31 -0500
From: Suravee Suthikulpanit <Suravee.Suthikulpanit@....com>
To: "Zheng, Lv" <lv.zheng@...el.com>,
"rjw@...ysocki.net" <rjw@...ysocki.net>,
"mika.westerberg@...ux.intel.com" <mika.westerberg@...ux.intel.com>,
"Moore, Robert" <robert.moore@...el.com>,
"hanjun.guo@...aro.org" <hanjun.guo@...aro.org>
CC: "lenb@...nel.org" <lenb@...nel.org>,
"hdegoede@...hat.com" <hdegoede@...hat.com>,
"tj@...nel.org" <tj@...nel.org>,
"mjg59@...f.ucam.org" <mjg59@...f.ucam.org>,
"gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
"al.stone@...aro.org" <al.stone@...aro.org>,
"graeme.gregory@...aro.org" <graeme.gregory@...aro.org>,
"leo.duran@....com" <leo.duran@....com>,
"linux-ide@...r.kernel.org" <linux-ide@...r.kernel.org>,
"linux-acpi@...r.kernel.org" <linux-acpi@...r.kernel.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"linaro-acpi@...ts.linaro.org" <linaro-acpi@...ts.linaro.org>
Subject: Re: [V8 PATCH 1/3] ACPICA: Add ACPI _CLS processing
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.)
The code introduced for supporting _CLS is also similar in the way
ACPICA is currently parsing the _CID or _SUB (which are also optional),
and using it for the same purpose of identifying devices for loading
drivers.
Also, since this method for identifying devices is OS-independent, I
believe this should not be done in the OSPM specific modules.
Thanks,
Suravee
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