On Tue, Jul 10, 2018 at 4:48 PM Arnd Bergmann <arnd@xxxxxxxx> wrote: > As Dave Chinner points out, we don't have a proper documentation for the > ktime_get() family of interfaces, making it rather unclear which of the > over 30 (!) interfaces one should actually use in a driver or elsewhere > in the kernel. > > I wrote up an explanation from how I personally see the interfaces, > documenting what each of the functions do and hopefully making it a bit > clearer which should be used where. > > This is the first time I tried writing .rst format documentation, so > in addition to any mistakes in the content, I probably also introduce > nonstandard formatting ;-) > > I first tried to add an extra section to > Documentation/timers/timekeeping.txt, but this is currently not included > in the generated API, and it seems useful to have the API docs as part > of what gets generated in > https://www.kernel.org/doc/html/latest/core-api/index.html#core-utilities > instead, so I started a new file there. > > I also considered adding the documentation inline in the > include/linux/timekeeping.h header, but couldn't figure out how to do > that in a way that would result both in helpful inline comments as > well as readable html output, so I settled for the latter, with > a small note pointing to it from the header. > > Cc: Dave Chinner <david@xxxxxxxxxxxxx> > Cc: John Stultz <john.stultz@xxxxxxxxxx> > Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx> > Cc: Stephen Boyd <sboyd@xxxxxxxxxx> > Cc: Linus Walleij <linus.walleij@xxxxxxxxxx> > Tested-by: Randy Dunlap <rdunlap@xxxxxxxxxxxxx> > Reviewed-by: Randy Dunlap <rdunlap@xxxxxxxxxxxxx> > Signed-off-by: Arnd Bergmann <arnd@xxxxxxxx> > --- > v2: minor changes suggested by Randy Reviewed-by: Linus Walleij <linus.walleij@xxxxxxxxxx> This brings into question commit bc2b7dab629a5 "iio:core: timestamping clock selection support" that has bothered me for some time. Now that is ABI, but we might be able to do some recommendations based on the time base and have a sensible default moving forward. As I want to make that clock base parsing similar for GPIO I first thought it was a good idea to support the same clocks, but now it seems like a bad idea. IIRC you told me to simply hammer down the clock that makes the most sense. At the same time userspace libraries (such as GNU radio) will be confused if they can't match the timestamping clocks, as correlating GPIO and IIO events is something they will want to do. And I guess these clocks are there for a reason. So asking Lars-Peter and Gregor: from a userspace point of view, what makes most sense for the usecases you have seen? Having one consistent time base or all of these as we currently have? Different clocks under different circumstances? Yours, Linus Walleij -- To unsubscribe from this list: send the line "unsubscribe linux-iio" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
