8:36 p.m.
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. 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(a)rjwysocki.net; Williams, Dan J
> Cc: Zheng, Lv; elliott(a)hpe.com; linux-nvdimm(a)lists.01.org; linux-
> acpi(a)vger.kernel.org; linux-kernel(a)vger.kernel.org; devel(a)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(a)rjwysocki.net; Williams, Dan J
> > > Cc: Moore, Robert; Zheng, Lv; elliott(a)hpe.com;
> > > linux-nvdimm(a)lists.01.or g; linux-acpi(a)vger.kernel.org;
> > > linux-kernel(a)vger.kernel.org; devel(a)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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