[PATCH 2/3] cyclic: make cyclic_register safe to call on already-registered info

[Stefan Roese]

On 07.05.25 12:58, Rasmus Villemoes wrote:
> Now that cyclic_unregister() is safe to call on a not-registered
> cyclic_info, we can make cyclic_register() behave like the mod_timer()
> and hrtimer_start() APIs in linux, in that they don't distinguish
> between whether the timer was already enabled or not; from the point
> of the call it is, with whatever timeout/period is set in that most
> recent call.
> 
> This avoids users of the cyclic API from separately keeping track of
> whether their callback is already registered or not, and even if they
> know it is, can be used for changing the period (and/or the callback
> function) without first doing unregister().
> 
> See also this recent'ish message from kernel maintainer Thomas
> Gleixner on that API design for timer frameworks:
> 
>    https://lore.kernel.org/lkml/87ikn6sibi.ffs@tglx/
> 
>    First of all the question is whether add() and mod() are really
>    valuable distinctions. I'm not convinced at all. Back then, when we
>    introduced hrtimers, we came to the conclusion that hrtimer_start()
>    is sufficient.
> 
> Signed-off-by: Rasmus Villemoes <ravi at prevas.dk>

Many thanks for digging into this and improving this cyclic interface
over the time.

Reviewed-by: Stefan Roese <sr at denx.de>

Thanks,
Stefan

> ---
>   common/cyclic.c | 2 ++
>   1 file changed, 2 insertions(+)
> 
> diff --git a/common/cyclic.c b/common/cyclic.c
> index 75662d9f613..ec952a01ee1 100644
> --- a/common/cyclic.c
> +++ b/common/cyclic.c
> @@ -43,6 +43,8 @@ static bool cyclic_is_registered(const struct cyclic_info *cyclic)
>   void cyclic_register(struct cyclic_info *cyclic, cyclic_func_t func,
>   		     uint64_t delay_us, const char *name)
>   {
> +	cyclic_unregister(cyclic);
> +
>   	memset(cyclic, 0, sizeof(*cyclic));
>   
>   	/* Store values in struct */

Viele Grüße,
Stefan Roese

-- 
DENX Software Engineering GmbH,      Managing Director: Erika Unter
HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany
Phone: (+49)-8142-66989-51 Fax: (+49)-8142-66989-80 Email: sr at denx.de