RE: [PATCH v2 1/3] ACPI/NFIT: Update Control Region Structure to comply ACPI 6.1

-----Original Message----- From: Toshi Kani [mailto:toshi.kani@hpe.com] Sent: Tuesday, March 01, 2016 9:37 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 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.

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 > N r y b X ǧv ^ )޺{.n + { i b {ay ʇڙ ,j f h z  w > j:+v w j m zZ+ ݢj" ! i