linux-kernel - Re: [PATCH v2 net-next 7/9] net: netdevsim: mimic tc-taprio offload

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Message-ID: <20230801174347.gtmxoqybhvbbl2rg@skbuf>
Date:   Tue, 1 Aug 2023 20:43:47 +0300
From:   Vladimir Oltean <vladimir.oltean@....com>
To:     Vinicius Costa Gomes <vinicius.gomes@...el.com>
Cc:     netdev@...r.kernel.org, "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Jamal Hadi Salim <jhs@...atatu.com>,
        Cong Wang <xiyou.wangcong@...il.com>,
        Jiri Pirko <jiri@...nulli.us>, linux-kernel@...r.kernel.org,
        intel-wired-lan@...ts.osuosl.org,
        Muhammad Husaini Zulkifli <muhammad.husaini.zulkifli@...el.com>,
        Peilin Ye <yepeilin.cs@...il.com>,
        Pedro Tammela <pctammela@...atatu.com>,
        Richard Cochran <richardcochran@...il.com>,
        Zhengchao Shao <shaozhengchao@...wei.com>,
        Maxim Georgiev <glipus@...il.com>
Subject: Re: [PATCH v2 net-next 7/9] net: netdevsim: mimic tc-taprio offload

On Tue, Aug 01, 2023 at 10:39:23AM -0700, Vinicius Costa Gomes wrote:
> Hi Vladimir,
> 
> Vladimir Oltean <vladimir.oltean@....com> writes:
> 
> > On Wed, Jun 14, 2023 at 05:06:24PM -0700, Vinicius Costa Gomes wrote:
> >> > +static int nsim_setup_tc_taprio(struct net_device *dev,
> >> > +				struct tc_taprio_qopt_offload *offload)
> >> > +{
> >> > +	int err = 0;
> >> > +
> >> > +	switch (offload->cmd) {
> >> > +	case TAPRIO_CMD_REPLACE:
> >> > +	case TAPRIO_CMD_DESTROY:
> >> > +		break;
> >> 
> >> I was thinking about how useful would proper validation of the
> >> parameters be? Thinking that we could detect "driver API" breakages
> >> earlier, and we want it documented that the drivers should check for the
> >> things that it supports.
> >> 
> >> Makes sense?
> >
> > Sorry, I lack imagination as to what the netdevsim driver may check for.
> > The taprio offload parameters should always be valid, properly speaking,
> > otherwise the Qdisc wouldn't be passing them on to the driver. At least
> > that would be the intention. The rest are hardware specific checks for
> > hardware specific limitations. Here there is no hardware.
> >
> 
> Trying to remember what was going through my mind when I said that.
> 
> What I seem to recall is something that would help us "keep honest":
> I was worrying about someone (perhaps myself ;-) sneaking a new feature
> in taprio and forgetting to update other drivers.
> 
> I thought that adding a check for the existing parameters would help
> detect those kind of things. If anything unknown was there in the
> offload struct, netdevsim would complain loudly.
> 
> Perhaps I was worrying too much. And the way to solve that is to keep
> active attention against that during review.

Ok, so I'm not making any change to the patch set as a result of this
comment, would you agree?