On Monday, July 06, 2015 03:53:14 PM Al Stone wrote:

On 07/03/2015 05:50 PM, Rafael J. Wysocki wrote:

quoted

On Friday, July 03, 2015 01:22:13 PM Al Stone wrote:

quoted

On 07/02/2015 11:23 PM, Hanjun Guo wrote:

quoted

Hi Rafael,

On 2015/7/3 8:21, Rafael J. Wysocki wrote:

quoted

On Thursday, July 02, 2015 05:48:34 PM Al Stone wrote:

quoted

Add the __ACPI_FADT_SPEC_VERSION() helper macro to build a proper version
number from a major and minor revision number.  Add also macros that use
the helper to construct the current version from the values in the FADT
(i.e., ACPI_FADT_SPEC_VERSION) and both the 5.1 and 6.0 versions.

These macros are added in order to simplify retrieving and comparing ACPI
specification version numbers, since this is becoming a more frequent need.
In particular, there are some architectures that require at least a certain
version of the spec, and there are differences in some structure sizes that
have changed with recent versions but can only be tracked by spec version
number.

Fixes: aeb823bbacc2 (ACPICA: ACPI 6.0: Add changes for FADT table.)
Signed-off-by: Al Stone <redacted>
---
 include/linux/acpi.h | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/include/linux/acpi.h b/include/linux/acpi.h
index c471dfc..0e525e8 100644
--- a/include/linux/acpi.h
+++ b/include/linux/acpi.h

@@ -48,6 +48,16 @@
 #include <acpi/acpi_io.h>
 #include <asm/acpi.h>
 
+#define __ACPI_FADT_SPEC_VERSION(major, minor) \
+	((unsigned int)major << 8 | (unsigned int)minor)
+
+#define ACPI_FADT_SPEC_VERSION	\
+	__ACPI_FADT_SPEC_VERSION(acpi_gbl_FADT.header.revision, \
+				 acpi_gbl_FADT.minor_revision)
+
+#define ACPI_FADT_SPEC_VERSION_51 __ACPI_FADT_SPEC_VERSION(5, 1)
+#define ACPI_FADT_SPEC_VERSION_60 __ACPI_FADT_SPEC_VERSION(6, 0)

I'd add underscores here, eg. ACPI_FADT_SPEC_VERSION_6_0

Agreed.

Will do.  This was a flip of the coin, on my part.

quoted

quoted

And what if there is 5.2 or even 5.3?

Hmm, do you mean in the future or just now? for both two cases,
only 5.1 and 5.1 errata (still has the same ACPI version with 5.1)
will be available, then jump to 6.0 and going forward if new versions
in the future.

I'm not sure if I understand your question correctly, if
not, please correct me :)

Thanks
Hanjun

I'm not sure I understand the question, either.  Traditionally, the
spec versioning has been exclusively linear -- i.e., now that 6.0
has replaced 5.1, there will be no more 5.x.  There may be errata
published (e.g., there was a 5.1A, and a 6.0A is forthcoming) but
the errata are not encoded in tables anywhere since they are meant
only as corrections to the base version.  This is unlikely to change,
but not impossible, of course :).

The only reason for putting in macros for 5.1 and 6.0 is that those
are the versions that I'm concerned with for this particular fix and
I know I will use them.  If others are needed, I'd have those that
need them add them.

It seems to me that you only need to compare acpi_gbl_FADT.header.revision
with 6 for this fix, though (if less than 6, use the old way, or use the
new way otherwise).

Isn't that the case?

Rafael

Ah, sorry for being a bit dense.  Yes, on arm64 we only support 5.1 or
later so for now, less than 6 is a sufficient test.  The 5.0 spec defines
yet a third size for the GICC subtable with the same MADT version number
(40 bytes) but we won't initialize ACPI if we have anything before 5.1.

OK

So, I could take this patch out of the set and reduce patch 2/3 somewhat
by just comparing against acpi_gbl_FADT.header.revision.  I think that's
what I'll do unless you think these macros have intrinsic value for other
reasons.

That would be fine by me, so please do it.

Thanks,
Rafael