linux-kernel - Re: [RFC PATCH 06/14] rtc-efi: register rtc-efi device when EFI enabled

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Date:	Fri, 20 Dec 2013 12:24:51 +0800
From:	joeyli <jlee@...e.com>
To:	Matt Fleming <matt@...sole-pimps.org>
Cc:	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	Alessandro Zummo <a.zummo@...ertech.it>,
	"H. Peter Anvin" <hpa@...or.com>,
	Matthew Garrett <matthew.garrett@...ula.com>, Elliott@...com,
	samer.el-haj-mahmoud@...com, Oliver Neukum <oneukum@...e.de>,
	werner@...e.com, trenn@...e.de, JBeulich@...e.com,
	linux-kernel@...r.kernel.org, rtc-linux@...glegroups.com,
	x86@...nel.org,
	"linux-efi@...r.kernel.org" <linux-efi@...r.kernel.org>,
	linux-acpi@...r.kernel.org, Matt Fleming <matt.fleming@...el.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>
Subject: Re: [RFC PATCH 06/14] rtc-efi: register rtc-efi device when EFI
 enabled

於 四，2013-12-19 於 14:09 +0000，Matt Fleming 提到：
> On Thu, 19 Dec, at 03:51:47PM, 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.
> > 
> > Cc: Matt Fleming <matt.fleming@...el.com>
> > Cc: H. Peter Anvin <hpa@...or.com>
> > Cc: Matthew Garrett <matthew.garrett@...ula.com>
> > Cc: Thomas Gleixner <tglx@...utronix.de>
> > Cc: Ingo Molnar <mingo@...hat.com>
> > Cc: Jan Beulich <JBeulich@...e.com>
> > Signed-off-by: Lee, Chun-Yi <jlee@...e.com>
> > ---
> >  arch/x86/platform/efi/efi.c |   17 +++++++++++++++++
> >  drivers/rtc/Kconfig         |    2 +-
> >  2 files changed, 18 insertions(+), 1 deletions(-)
> 
> This patch needs to be justified. Enabling the EFI runtime *Time
> functions just because they're available isn't good enough. We need to
> know why this patch improves things, what use case does it solve?
> 

The main purpose of enable efi-rtc driver is providing interface to
userspace access timezone field in EFI time services.

Currently have two BIOS interfaces provided the timezone field accessing
ability, ACPI TAD and EFI. I hope can enable them on x86_64 machines.

> The general attitude has been that we want to invoke the runtime
> services less, not more, due to the huge variety of runtime
> implementation bugs.
> 

I agreed, but userspace application should not be too often to access
RTC. Maybe only when system boot and set timezone.


Thanks a lot!
Joey Lee

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