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Message-Id: <B7D3442E-3874-488A-9A01-C126BAFF9A88@kernel.crashing.org> Date: Wed, 26 Jul 2006 01:26:07 +0200 From: Segher Boessenkool <segher@...nel.crashing.org> To: Neil Horman <nhorman@...driver.com> Cc: "H. Peter Anvin" <hpa@...or.com>, linux-kernel@...r.kernel.org, a.zummo@...ertech.it, jg@...edesktop.org Subject: Re: [PATCH] RTC: Add mmap method to rtc character driver >> But userland cannot know if there is a more efficient option to >> use than this /dev/rtc way, without using VDSO/vsyscall. >> > Sure, but detecting if /dev/rtc via mmap is faster than > gettimeofday is an > orthogonal issue to having the choice in the first place. No it's not. Userland can not detect things it doesn't know about, and then when there is a great choice, it won't see it, and use the 6000kW solution (or any other really bad thing) instead. Using the old old legacy stuff when there's nothing better around is a fine idea; please just implement an x86 VDSO that does just that. x86 is what you care about IIUC. Don't saddle up non-x86 systems that just happen to have a legacy RTC around, and perhaps x86 systems that don't sanely expose their better interfaces, with this quite suboptimal solution for years to come. Segher - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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