Re: [PATCH 1/3] rtc-efi: register rtc-efi device when EFI enabled
From: H. Peter Anvin
Date: Fri Dec 28 2012 - 15:41:20 EST
On 12/28/2012 11:17 AM, Matthew Garrett wrote:
On Fri, 2012-12-28 at 11:07 -0800, H. Peter Anvin wrote:
We do have such machines, which is why this change has been reverted twice already. I believe we should stick to the priority scheme I proposed a few weeks ago.
I seem to have missed that discussion, and couldn't find it after a
brief search. Got a pointer?
Looks like it was a non-public distribution ... anyway, what I wrote was:
I suspect that what we *should* do looks like:
1. If ACPI exports a Time and Alarm Device (ACPI000E) the use it;
2. If ACPI exports an PC/AT device (PNP0B00/1/2) then use it(*);
3. If we have an EFI RTC use it;
4. Probe for a PC/AT RTC device.
I'm unsure what the ordering of 1 & 2 should be. The ACPI device has
the advantage that it contains time zone information, which is important
for Windows interoperability, and at least optionally supports
millisecond resolution; there is no way to even export "this is where
you find time zone information" (since we're dealing with an RTC with
embedded CMOS, there is storage available, it is just a matter of
telling the OS how to find it) for the PNP0B0x devices.
The TAD is also guaranteed to map 1:1 to the EFI RTC.
-hpa
--
H. Peter Anvin, Intel Open Source Technology Center
I work for Intel. I don't speak on their behalf.
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