Messages in this thread | | | From | Arnd Bergmann <> | Date | Mon, 20 Apr 2020 16:38:32 +0200 | Subject | Re: [PATCH] net: cpts: Condition WARN_ON on PTP_1588_CLOCK |
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On Mon, Apr 20, 2020 at 11:38 AM Clay McClure <clay@daemons.net> wrote: > On Thu, Apr 16, 2020 at 02:11:45PM +0300, Grygorii Strashko wrote: > > > > CPTS_MOD merely implies PTP_1588_CLOCK; it is possible to build cpts > > > without PTP clock support. In that case, ptp_clock_register() returns > > > NULL and we should not WARN_ON(cpts->clock) when downing the interface. > > > The ptp_*() functions are stubbed without PTP_1588_CLOCK, so it's safe > > > to pass them a null pointer. > > > > Could you explain the purpose of the exercise (Enabling CPTS with > > PTP_1588_CLOCK disabled), pls? > > Hardware timestamping with a free-running PHC _almost_ works without > PTP_1588_CLOCK, but since PHC rollover is handled by the PTP kworker > in this driver the timestamps end up not being monotonic. > > And of course the moment you want to syntonize/synchronize the PHC with > another clock (say, CLOCK_REALTIME), you'll need a PTP clock device. So > you're right, there's not much point in building CPTS_MOD without > PTP_1588_CLOCK. > > Given that, I wonder why all the Ethernet drivers seem to just `imply` > PTP_1588_CLOCK, rather than `depends on` it?
I suspect we should move all of them back. This was an early user of 'imply', but the meaning of that keyword has now changed in the latest Kconfig.
> diff --git a/drivers/net/ethernet/ti/cpts.c b/drivers/net/ethernet/ti/cpts.c > index 10ad706dda53..70b15039cd37 100644 > --- a/drivers/net/ethernet/ti/cpts.c > +++ b/drivers/net/ethernet/ti/cpts.c > @@ -462,8 +462,8 @@ int cpts_register(struct cpts *cpts) > timecounter_init(&cpts->tc, &cpts->cc, ktime_get_real_ns()); > > cpts->clock = ptp_clock_register(&cpts->info, cpts->dev); > - if (IS_ERR(cpts->clock)) { > - err = PTR_ERR(cpts->clock); > + if (IS_ERR_OR_NULL(cpts->clock)) { > + err = cpts->clock ? PTR_ERR(cpts->clock) : -EOPNOTSUPP; > cpts->clock = NULL; > goto err_ptp;
Something else is wrong if you need IS_ERR_OR_NULL(). Any kernel interface should either return an negative error code when something goes wrong, or should return NULL for all errors, but not mix the two.
Arnd
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