Date: Thu, 14 Feb 2013 15:03:48 +0100 From: =?utf-8?Q?Dag-Erling_Sm=C3=B8rgrav?= <des@des.no> To: Andriy Gapon <avg@FreeBSD.org> Cc: Adrian Chadd <adrian@FreeBSD.org>, freebsd-arch@FreeBSD.org Subject: Re: Proposal: Unify printing the function name in panic messages() Message-ID: <86mwv7q9ff.fsf@ds4.des.no> In-Reply-To: <511C002C.8090801@FreeBSD.org> (Andriy Gapon's message of "Wed, 13 Feb 2013 23:05:48 %2B0200") References: <201302120134.r1C1Ycfh026347@chez.mckusick.com> <CAJ-Vmo=wwFD7_OF%2BFdJkPyxjQD_4y-yBU6guUHTuCkFr%2BoYh-w@mail.gmail.com> <201302131504.19142.jhb@freebsd.org> <201302131511.14019.jhb@freebsd.org> <CAJ-Vmong=OW-243rVYh%2BWc4dwQDWbynHkKcEr3Zp3RD2-2_L4g@mail.gmail.com> <511C002C.8090801@FreeBSD.org>
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Andriy Gapon <avg@FreeBSD.org> writes: > Something of tangential relevance. In Linux they have some special > trace code to debug ACPI resume issues that stores some IDs/hashes of > trace statements (perhaps somewhat akin to our ktr) to RTC time-of-day > registers. I guess that that was a smart choice because you can count > on presence of those registers and they can be written with simple > outb instructions. They're not really registers, just unused space in non-volatile memory. To the computer, a DS1307-compatible RTC looks like a 64-byte flash chip connected by I2C. IIRC, the RTC stores the date and time in BCD in the lower bytes and the rest is unused, unless you have a high-end chip that uses a few extra bytes to store calibration parameters etc. Storing data there is not *quite* "simple outb instructions" since I2C is an adressable serial bus, but it's not insurmountable, and the type of machines that matter to people working on suspend / resume are pretty much guaranteed to have a DS1307-compatible RTC. DES --=20 Dag-Erling Sm=C3=B8rgrav - des@des.no
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