Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753225AbbF3VP0 (ORCPT ); Tue, 30 Jun 2015 17:15:26 -0400 Received: from mail-ig0-f172.google.com ([209.85.213.172]:36529 "EHLO mail-ig0-f172.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753176AbbF3VPR (ORCPT ); Tue, 30 Jun 2015 17:15:17 -0400 Message-ID: <559306E2.7000901@linaro.org> Date: Tue, 30 Jun 2015 15:15:14 -0600 From: Al Stone User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.7.0 MIME-Version: 1.0 To: "Rafael J. Wysocki" CC: ACPI Devel Maling List , "linux-arm-kernel@lists.infradead.org" , "Rafael J. Wysocki" , Len Brown , Catalin Marinas , Will Deacon , Thomas Gleixner , Jason Cooper , Linux Kernel Mailing List , "linaro-acpi@lists.linaro.org" , Lists linaro-kernel , "patches@linaro.org" Subject: Re: [PATCH v2 1/3] ACPI : introduce macros for using the ACPI specification version References: <1434666968-1543-1-git-send-email-al.stone@linaro.org> <1434666968-1543-2-git-send-email-al.stone@linaro.org> In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2544 Lines: 74 On 06/30/2015 02:12 PM, Rafael J. Wysocki wrote: > Hi Al, > > On Fri, Jun 19, 2015 at 12:36 AM, Al Stone wrote: >> Add the ACPI_SPEC_VERSION() macro to build a proper version number from >> a major and minor revision number. Add also the ACPI_FADT_SPEC_VERSION >> that constructs a proper version number from the entries in the current >> FADT. >> >> 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. >> >> Signed-off-by: Al Stone >> --- >> include/linux/acpi.h | 5 +++++ >> 1 file changed, 5 insertions(+) >> >> diff --git a/include/linux/acpi.h b/include/linux/acpi.h >> index a4acb55..33ed313 100644 >> --- a/include/linux/acpi.h >> +++ b/include/linux/acpi.h >> @@ -48,6 +48,11 @@ >> #include >> #include >> >> +#define ACPI_SPEC_VERSION(major, minor) ((major<<8)|minor) > > One nit here. > > acpi_gbl_FADT.header.revision is of type u8 originally, so shifting it > by 8 bit positions only works due to some implicit type casting I > suppose. Bah. That was being sloppy on my part. Sorry about that. Will fix. > Moreover, it is not entirely clear why the macro is specific to the > computation of the ACPI spec version. As far as I know, that's the only way to extract the spec version from tables; I don't recall there being any other table with that info. Since I will likely use this again, it seemed to make sense at the time. > So I'd drop ACPI_SPEC_VERSION and only define ACPI_FADT_SPEC_VERSION > as something like > > #define ACPI_FADT_SPEC_VERSION (((unsigned > int)acpi_gbl_FADT.header.revision << 8) | (unsigned > int)acpi_gbl_FADT.minor_revision) > > Thanks, > Rafael > Sure. That makes sense. It makes it clearer that this is the version just from the FADT. I'll do that. -- ciao, al ----------------------------------- Al Stone Software Engineer Linaro Enterprise Group al.stone@linaro.org ----------------------------------- -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/