linux-kernel - Re: [PATCH 1/3] rtc-efi: register rtc-efi device when EFI enabled

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Date:	Tue, 08 Jan 2013 22:27:36 -0800
From:	"H. Peter Anvin" <hpa@...or.com>
To:	joeyli <jlee@...e.com>
CC:	Matthew Garrett <matthew.garrett@...ula.com>,
	"matt.fleming@...el.com" <matt.fleming@...el.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-efi@...r.kernel.org" <linux-efi@...r.kernel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>, Jan Beulich <JBeulich@...e.com>
Subject: Re: [PATCH 1/3] rtc-efi: register rtc-efi device when EFI enabled

That makes it even less compelling...

joeyli <jlee@...e.com> wrote:

>於 五，2012-12-28 於 17:07 -0800，H. Peter Anvin 提到：
>> On 12/28/2012 05:00 PM, joeyli wrote:
>> > 於 五，2012-12-28 於 17:43 +0000，Matthew Garrett 提到：
>> >> On Sat, 2012-12-29 at 00:26 +0800, Lee, Chun-Yi wrote:
>> >>> UEFI time services, GetTime(), SetTime(), GetWakeupTime(),
>SetWakeupTime() are also
>> >>> supported by other non-IA64 architecutre with UEFI BIOS, e.g.
>x86.
>> >>>
>> >>> This patch changed RTC_DRV_EFI configuration to depend on EFI but
>not just IA64. It
>> >>> checks efi_enabled flag and efi-rtc driver should enabled.
>> >>
>> >> In theory, certainly - but do we still have machines that explode
>if the
>> >> get_time call is made? We may also want to think about disabling
>the
>> >> legacy access to the RTC if the EFI calls are present.
>> > 
>> > The legacy get_time access on my test machine is work fine, not
>thing
>> > explode. :-)
>> > Just we have a function want to expose the timezone information to
>> > userspace and also store it.
>> > 
>> 
>> We should indeed save the timezone information if it is available --
>> either from the ACPI TAD or from the EFI RTC, or even via some
>> platform-dependent mechanism.  It is important, though, that that is
>> separate from the order of priority.
>> 
>> 	-hpa
>> 
>
>I found Windows 8 doesn't aware/maintain the Timezone and Daylight
>fields in EFI_TIME struct.
>
>I got a Acer UEFI notebook and I keep the Windows 8 hard drive
>(/dev/sda) but install Linux to another hard drive (/dev/sdb). 
>
>On Linux, I applied my rtc-efi patches for allow user space feed
>Timezone and store it to BIOS through SetTime(). I wrote a simple user
>space program to set Timezone and Daylight fields, after set those
>fields I reboot to Windows 8 and use DateTime setting GUI to look at
>the
>change. Looks Windows doesn't aware the change, it just assume the time
>in DateTime filed is local time, but didn't show the Timezone that was
>set by me on Linux to GUI.
>
>Then, I select another Timezone(country) through Windows 8 GUI, and
>reboot to Linux. I read the Timezone and Daylight by program but didn't
>see the Timezone and Daylight changed by Windows 8, the value is still
>the same with my latest time setting by Linux program. Windows 8
>changed
>DayTime fields but didn't maintain Timezone and Daylight.
>
>I only have this machine with preloaded Windows 8 for verify the
>behavior, not sure it's normally or not. If Windows 8 ignores Timezone
>and Daylight fields in UEFI BIOS, then I think it's lower down the
>necessary for we maintain Timezone and Daylight in UEFI BIOS. 
>
>We still can store Timezone and Daylight value to UEFI, but will have
>no
>any interactive with Windows 8.
>
>Appreciate for any suggestions.
>
>
>Thanks a lot!
>Joey Lee

-- 
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