netdev - Re: [PATCH net v3 1/2] taprio: Fix enabling offload with wrong number of traffic classes

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Message-ID: <20200131072453.454930eb@cakuba.hsd1.ca.comcast.net>
Date:   Fri, 31 Jan 2020 07:24:53 -0800
From:   Jakub Kicinski <kuba@...nel.org>
To:     Vinicius Costa Gomes <vinicius.gomes@...el.com>
Cc:     netdev@...r.kernel.org, jhs@...atatu.com, xiyou.wangcong@...il.com,
        jiri@...nulli.us, davem@...emloft.net, vladimir.oltean@....com,
        po.liu@....com
Subject: Re: [PATCH net v3 1/2] taprio: Fix enabling offload with wrong
 number of traffic classes

On Wed, 29 Jan 2020 17:37:20 -0800, Vinicius Costa Gomes wrote:
> If the driver implementing taprio offloading depends on the value of
> the network device number of traffic classes (dev->num_tc) for
> whatever reason, it was going to receive the value zero. The value was
> only set after the offloading function is called.
> 
> So, moving setting the number of traffic classes to before the
> offloading function is called fixes this issue. This is safe because
> this only happens when taprio is instantiated (we don't allow this
> configuration to be changed without first removing taprio).
> 
> Fixes: 9c66d1564676 ("taprio: Add support for hardware offloading")
> Reported-by: Po Liu <po.liu@....com>
> Signed-off-by: Vinicius Costa Gomes <vinicius.gomes@...el.com>
> Acked-by: Vladimir Oltean <vladimir.oltean@....com>

What about Dave's question about resetting the tc state with
netdev_reset_tc()?