From: "Moore, Robert" <robert.moore@intel.com>
To: Toshi Kani <toshi.kani@hpe.com>, "rjw@rjwysocki.net" <rjw@rjwysocki.net>,
        "Williams, Dan J" <dan.j.williams@intel.com>
CC: "Zheng, Lv" <lv.zheng@intel.com>, "elliott@hpe.com" <elliott@hpe.com>,
        "linux-nvdimm@lists.01.org" <linux-nvdimm@ml01.01.org>,
        "linux-acpi@vger.kernel.org" <linux-acpi@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "devel@acpica.org" <devel@acpica.org>
Subject: RE: [PATCH v2 1/3] ACPI/NFIT: Update Control Region Structure to
 comply ACPI 6.1
Thread-Topic: [PATCH v2 1/3] ACPI/NFIT: Update Control Region Structure to
 comply ACPI 6.1
Thread-Index: AQHRbbRts80XXzttYEOOULqVyeHP1J9Evf0wgACeKgD//2/VAIAAoKGA//95QFA=
Date: Tue, 1 Mar 2016 17:37:01 +0000
Message-ID: <94F2FBAB4432B54E8AACC7DFDE6C92E37E44D782@ORSMSX110.amr.corp.intel.com>
References: <1456178130-26468-1-git-send-email-toshi.kani@hpe.com>
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> -----Original Message-----
> From: Toshi Kani [mailto:toshi.kani@hpe.com]
> Sent: Tuesday, March 01, 2016 9:37 AM
> To: Moore, Robert; rjw@rjwysocki.net; Williams, Dan J
> Cc: Zheng, Lv; elliott@hpe.com; linux-nvdimm@lists.01.org; linux-
> acpi@vger.kernel.org; linux-kernel@vger.kernel.org; devel@acpica.org
> Subject: Re: [PATCH v2 1/3] ACPI/NFIT: Update Control Region Structure to
> comply ACPI 6.1
> 
> On Tue, 2016-03-01 at 16:03 +0000, Moore, Robert wrote:
> > We have a bunch of macros in include/acmacros.h -- like this:
> >
> > ACPI_MOVE_16_TO_16(d, s)
> 
> There is a problem in using the ACPICA byte-swap macros.  ACPI is little-
> endian arch, so the macros are set to perform byte-swappings when the CPU
> arch is big-endian.  This case, however, is the other way around.  The
> fields in question are defined & stored as arrays of bytes.

That's not what I see in the ACPI spec. The fields are defined like any other ACPI table.

Vendor ID 2 6 
Identifier indicating the vendor of the NVDIMM.
This field shall be set to the value of the NVDIMM SPD Module
Manufacturer ID Code field a with byte 0 set to DDR4 SPD byte
320 and byte 1 set to DDR4 SPD byte 321.

Device ID 2 8
Identifier for the NVDIMM, assigned by the module vendor.
This field shall be set to the value of the NVDIMM SPD Module
Product Identifier field b with byte 0 set to SPD byte 192 and
byte 1 set to SPD byte 193.

Revision ID 2 10 
Revision of the NVDIMM, assigned by the module vendor.
Byte 1 of this field is reserved.
Byte 0 of this field shall be set to the value of the NVDIMM SPD
Module Revision Code field a (i.e., SPD byte 349).


Etc.


If you treat
> them as multi-bytes numeric values, then you need to byte-swap them when
> the CPU arch is little-endian because arrays of bytes have the same
> addressing as big-endian.
> 
> Another issue is that it is not clear who needs to perform the byte-
> swapping among ACPICA and drivers.  If ACPICA, drivers must agree that
> these fields are always treated as multi-bytes numeric values despite of
> the spec.  If drivers, we need to make sure that only a single driver
> performs this byte-swapping one time as ACPI tables are global structures.
> 
> I think it is much clearer to define the structure according to the ACPI
> spec.
> 
> Thanks,
> -Toshi
> 
> > > -----Original Message-----
> > > From: Toshi Kani [mailto:toshi.kani@hpe.com]
> > > Sent: Tuesday, March 01, 2016 8:38 AM
> > > To: Moore, Robert; rjw@rjwysocki.net; Williams, Dan J
> > > Cc: Zheng, Lv; elliott@hpe.com; linux-nvdimm@lists.01.org; linux-
> > > acpi@vger.kernel.org; linux-kernel@vger.kernel.org; devel@acpica.org
> > > Subject: Re: [PATCH v2 1/3] ACPI/NFIT: Update Control Region
> > > Structure to comply ACPI 6.1
> > >
> > > On Tue, 2016-03-01 at 15:13 +0000, Moore, Robert wrote:
> > > >
> > > > > -----Original Message-----
> > > > > From: Toshi Kani [mailto:toshi.kani@hpe.com]
> > > > > Sent: Monday, February 22, 2016 1:55 PM
> > > > > To: rjw@rjwysocki.net; Williams, Dan J
> > > > > Cc: Moore, Robert; Zheng, Lv; elliott@hpe.com;
> > > > > linux-nvdimm@lists.01.or g; linux-acpi@vger.kernel.org;
> > > > > linux-kernel@vger.kernel.org; devel@acpica.org; Toshi Kani
> > > > > Subject: [PATCH v2 1/3] ACPI/NFIT: Update Control Region
> > > > > Structure to comply ACPI 6.1
> > > > >
> > > > > ACPI 6.1, Table 5-133, updates NVDIMM Control Region Structure
> > > > > as follows.
> > > > >  - Valid Fields, Manufacturing Location, and Manufacturing Date
> > > > >    are added from reserved range.  No change in the structure
> size.
> > > > >  - IDs defined as SPD values are arrays of bytes.  The spec
> > > > >    clarified that they need to be represented as arrays of bytes
> > > > >    as well.
> > > > >
> > > > > This patch makes the following changes to support this update.
> > > > >  - Change 'struct acpi_nfit_control_region' to reflect the update.
> > > > >    SPD IDs are defined as arrays of bytes, so that they can be
> > > > >    treated in the same way regardless of CPU endianness and are
> > > > >    not miss-treated as little-endian numeric values.
> > > >
> > > >
> > > > I don't think we are going to start changing the ACPI tables
> > > > defined in the ACPICA headers because of this. We do in fact have
> > > > macros for this purpose.
> > >
> > > Can you elaborate what macros you suggest to use for this purpose?
> > >
> > > Thanks,
> > > -Toshi
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