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

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Date: Tue, 01 Aug 2023 11:06:46 -0700
From: Vinicius Costa Gomes <vinicius.gomes@...el.com>
To: Vladimir Oltean <vladimir.oltean@....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

Vladimir Oltean <vladimir.oltean@....com> writes:

> 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?

Agreed.

Cheers,
-- 
Vinicius