netdev - RE: [PATCH net-next 3/4] dpll: netlink/core: add support for pin-dpll signal phase offset/adjust

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Date: Mon, 2 Oct 2023 14:32:30 +0000
From: "Kubalewski, Arkadiusz" <arkadiusz.kubalewski@...el.com>
To: Vadim Fedorenko <vadim.fedorenko@...ux.dev>, "netdev@...r.kernel.org"
	<netdev@...r.kernel.org>
CC: "jiri@...nulli.us" <jiri@...nulli.us>, "corbet@....net" <corbet@....net>,
	"davem@...emloft.net" <davem@...emloft.net>, "kuba@...nel.org"
	<kuba@...nel.org>, "pabeni@...hat.com" <pabeni@...hat.com>, "Brandeburg,
 Jesse" <jesse.brandeburg@...el.com>, "Nguyen, Anthony L"
	<anthony.l.nguyen@...el.com>, "linux-doc@...r.kernel.org"
	<linux-doc@...r.kernel.org>, "intel-wired-lan@...ts.osuosl.org"
	<intel-wired-lan@...ts.osuosl.org>
Subject: RE: [PATCH net-next 3/4] dpll: netlink/core: add support for pin-dpll
 signal phase offset/adjust

>From: Vadim Fedorenko <vadim.fedorenko@...ux.dev>
>Sent: Wednesday, September 27, 2023 8:09 PM
>
>On 27/09/2023 10:24, Arkadiusz Kubalewski wrote:
>> Add callback op (get) for pin-dpll phase-offset measurment.
>> Add callback ops (get/set) for pin signal phase adjustment.
>> Add min and max phase adjustment values to pin proprties.
>> Invoke get callbacks when filling up the pin details to provide user
>> with phase related attribute values.
>> Invoke phase-adjust set callback when phase-adjust value is provided for
>> pin-set request.
>>
>> Signed-off-by: Arkadiusz Kubalewski <arkadiusz.kubalewski@...el.com>
>
>[...]
>
>> +static int
>> +dpll_pin_phase_adj_set(struct dpll_pin *pin, struct nlattr
>> *phase_adj_attr,
>> +		       struct netlink_ext_ack *extack)
>> +{
>> +	struct dpll_pin_ref *ref;
>> +	unsigned long i;
>> +	s32 phase_adj;
>> +	int ret;
>> +
>> +	phase_adj = nla_get_s32(phase_adj_attr);
>> +	if (phase_adj > pin->prop->phase_range.max ||
>> +	    phase_adj < pin->prop->phase_range.min) {
>> +		NL_SET_ERR_MSG(extack, "phase adjust value not supported");
>> +		return -EINVAL;
>> +	}
>> +	xa_for_each(&pin->dpll_refs, i, ref) {
>> +		const struct dpll_pin_ops *ops = dpll_pin_ops(ref);
>> +		struct dpll_device *dpll = ref->dpll;
>> +
>> +		if (!ops->phase_adjust_set)
>> +			return -EOPNOTSUPP;
>
>I'm thinking about this part. We can potentially have dpll devices with
>different expectations on phase adjustments, right? And if one of them
>won't be able to adjust phase (or will fail in the next line), then
>netlink will return EOPNOTSUPP while _some_ of the devices will be
>adjusted. Doesn't look great. Can we think about different way to apply
>the change?
>

Well makes sense to me.

Does following makes sense as a fix?
We would call op for all devices which has been provided with the op.
If device has no op -> add extack error, continue
If device fails to set -> add extack error, continue
Function always returns 0.

Thank you!
Arkadiusz

>
>> +		ret = ops->phase_adjust_set(pin,
>> +					    dpll_pin_on_dpll_priv(dpll, pin),
>> +					    dpll, dpll_priv(dpll), phase_adj,
>> +					    extack);
>> +		if (ret)
>> +			return ret;
>> +	}
>> +	__dpll_pin_change_ntf(pin);
>> +
>> +	return 0;
>> +}
>> +