linux-kernel - Re: [PATCH v2 net-next 3/9] net: enetc: only commit preemptible TCs to hardware when MM TX is active

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Date:   Thu, 20 Apr 2023 19:34:53 +0300
From:   Vladimir Oltean <vladimir.oltean@....com>
To:     Simon Horman <simon.horman@...igine.com>
Cc:     netdev@...r.kernel.org, "David S. Miller" <davem@...emloft.net>,
        Michal Kubecek <mkubecek@...e.cz>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Claudiu Manoil <claudiu.manoil@....com>,
        Xiaoliang Yang <xiaoliang.yang_1@....com>,
        Petr Machata <petrm@...dia.com>,
        Danielle Ratson <danieller@...dia.com>,
        Pranavi Somisetty <pranavi.somisetty@....com>,
        Harini Katakam <harini.katakam@....com>,
        Vinicius Costa Gomes <vinicius.gomes@...el.com>,
        Kurt Kanzenbach <kurt@...utronix.de>,
        Gerhard Engleder <gerhard@...leder-embedded.com>,
        Ferenc Fejes <ferenc.fejes@...csson.com>,
        Aaron Conole <aconole@...hat.com>,
        linux-kselftest@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 net-next 3/9] net: enetc: only commit preemptible TCs
 to hardware when MM TX is active

On Thu, Apr 20, 2023 at 04:42:52PM +0200, Simon Horman wrote:
> > +	/* This will time out after the standard value of 3 verification
> > +	 * attempts. To not sleep forever, it relies on a non-zero verify_time,
> > +	 * guarantee which is provided by the ethtool nlattr policy.
> > +	 */
> > +	return read_poll_timeout(enetc_port_rd, val,
> > +				 ENETC_MMCSR_GET_VSTS(val) == 3,
> 
> nit: 3 is doing a lot of work here.
>      As a follow-up, perhaps it could become part of an enum?

IMHO it's easy to abuse enums, when numbers could do just fine. I think
that in context (seeing the entire enetc_ethtool.c), this is not as bad
as just this patch makes it to be, because the other occurrence of
ENETC_MMCSR_GET_VSTS() is:

	switch (ENETC_MMCSR_GET_VSTS(val)) {
	case 0:
		state->verify_status = ETHTOOL_MM_VERIFY_STATUS_DISABLED;
		break;
	case 2:
		state->verify_status = ETHTOOL_MM_VERIFY_STATUS_VERIFYING;
		break;
	case 3:
		state->verify_status = ETHTOOL_MM_VERIFY_STATUS_SUCCEEDED;
		break;
	case 4:
		state->verify_status = ETHTOOL_MM_VERIFY_STATUS_FAILED;
		break;
	case 5:
	default:
		state->verify_status = ETHTOOL_MM_VERIFY_STATUS_UNKNOWN;
		break;
	}

so it's immediately clear what the 3 represents (in vim I just press '*'
to see the other occurrences of ENETC_MMCSR_GET_VSTS).

I considered it, but I don't feel an urgent necessity to add an enum here.
Doing that would essentially transform the code into:

	return read_poll_timeout(enetc_port_rd, val,
				 ENETC_MMCSR_GET_VSTS(val) == ENETC_MM_VSTS_SUCCEEDED,

	switch (ENETC_MMCSR_GET_VSTS(val)) {
	case ENETC_MMCSR_VSTS_DISABLED:
		state->verify_status = ETHTOOL_MM_VERIFY_STATUS_DISABLED;
		break;
	case ENETC_MMCSR_VSTS_VERIFYING:
		state->verify_status = ETHTOOL_MM_VERIFY_STATUS_VERIFYING;
		break;
	case ENETC_MMCSR_VSTS_SUCCEEDED:
		state->verify_status = ETHTOOL_MM_VERIFY_STATUS_SUCCEEDED;
		break;
	case ENETC_MMCSR_VSTS_FAILED:
		state->verify_status = ETHTOOL_MM_VERIFY_STATUS_FAILED;
		break;
	case ENETC_MMCSR_VSTS_UNKNOWN:
	default:
		state->verify_status = ETHTOOL_MM_VERIFY_STATUS_UNKNOWN;
		break;
	}

which to my eye is more bloated.