Re: [PATCH 7/9] RFC: rtc: implement rtc_read_timeval()

From: Alexander Holler
Date: Fri Jun 14 2013 - 13:44:15 EST

Am 14.06.2013 19:23, schrieb John Stultz:
On 06/14/2013 09:52 AM, Alexander Holler wrote:
Some RTCs offer a higher resolution than seconds. To support reading such
high resolution timestamps from inside the kernel implement
rtc_read_timeval() and add a read_timeval to the rtc-ops.

So I like the direction this patch is going. But if we're going to add a
new interface, lets not use an already out-dated structure (timeval).

Instead could you rework this to be timepsec based? Or ktime_t if its
really internal only?

Sure, no problem. I wasn't aware timeval is out-dated and I've read somewhere in the sources a comment that ktime_t has to disappear. I had no clue if I should use timeval or timespec, and just have roled a dice to decide between timeval and timespec.

That "internal only" is only because I don't want to write changes for the userspace api to handle RTCs with greater precision than seconds. I don't have a writable RTC supporting such a precision and I want to leave this for people which are developing such devices and earning money with them.

Besides that, I have almost no knowledge about the userspace api for RTCs. If just looked a bit around in the in-kernel-ntp-sources for adjtimex, but that's all.

Please don't forget, my only motivation is to use an USB-RTC I've build myself to use with developer-boards without RTCs. All the other work like the support for higher precisions, the new hctosys or similiar is just because I let me trick to do that ;)


Alexander Holler
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