Messages in this thread | | | From | Mahesh Bandewar (महेश बंडेवार) <> | Date | Mon, 2 Oct 2023 17:12:36 -0700 | Subject | Re: [PATCH 1/4] time: add ktime_get_cycles64() api |
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On Fri, Sep 29, 2023 at 12:07 AM John Stultz <jstultz@google.com> wrote: > > On Thu, Sep 28, 2023 at 11:56 PM John Stultz <jstultz@google.com> wrote: > > On Thu, Sep 28, 2023 at 11:35 PM Mahesh Bandewar (महेश बंडेवार) > > <maheshb@google.com> wrote: > > > On Thu, Sep 28, 2023 at 10:15 PM John Stultz <jstultz@google.com> wrote: > > > > 3) Nit: The interface is called ktime_get_cycles64 (timespec64 > > > > returning interfaces usually are postfixed with ts64). > > > > > > > Ah, thanks for the explanation. I can change to comply with the > > > convention. Does ktime_get_cycles_ts64() make more sense? > > > > Maybe a little (it at least looks consistent), but not really if > > you're sticking raw cycles in the timespec :) > > > > Despite my concerns that it's a bad idea, If one was going to expose > raw cycles from the timekeeping core, I'd suggest doing so directly as > a u64 (`u64 ktime_get_cycles(void)`). > > That may mean widening (or maybe using a union in) your PTP ioctl data > structure to have a explicit cycles field. > Or introducing a separate ioctl that deals with cycles instead of timespec64s. > > Squeezing data into types that are canonically used for something else > should always be avoided if possible (there are some cases where > you're stuck with an existing interface, but that's not the case > here). > > But I still think we should avoid exporting the raw cycle values > unless there is some extremely strong argument for it (and if we can, > they should be abstracted into some sort of cookie value to avoid > userland using it as a raw clock). > Thanks for the input John. This change is basically to address the API gap and allow it to give a user-given timebase for the sandwich time. I will remove this RAW-CYCLES option for now. If it's deemed necessary, we can always add it later into the same API.
> thanks > -john
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