netdev - Re: [PATCH iwl-next v5 9/9] igc: Block setting preemptible traffic class in taprio

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Message-ID: <20250220112848.wpoeqp5bplgkyg73@skbuf>
Date: Thu, 20 Feb 2025 13:28:48 +0200
From: Vladimir Oltean <vladimir.oltean@....com>
To: Faizal Rahim <faizal.abdul.rahim@...ux.intel.com>
Cc: Tony Nguyen <anthony.l.nguyen@...el.com>,
	Przemek Kitszel <przemyslaw.kitszel@...el.com>,
	Andrew Lunn <andrew+netdev@...n.ch>,
	"David S . Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	Maxime Coquelin <mcoquelin.stm32@...il.com>,
	Alexandre Torgue <alexandre.torgue@...s.st.com>,
	Simon Horman <horms@...nel.org>,
	Russell King <linux@...linux.org.uk>,
	Alexei Starovoitov <ast@...nel.org>,
	Daniel Borkmann <daniel@...earbox.net>,
	Jesper Dangaard Brouer <hawk@...nel.org>,
	John Fastabend <john.fastabend@...il.com>,
	Furong Xu <0x1207@...il.com>,
	Russell King <rmk+kernel@...linux.org.uk>,
	Serge Semin <fancer.lancer@...il.com>,
	Xiaolei Wang <xiaolei.wang@...driver.com>,
	Suraj Jaiswal <quic_jsuraj@...cinc.com>,
	Kory Maincent <kory.maincent@...tlin.com>,
	Gal Pressman <gal@...dia.com>,
	Jesper Nilsson <jesper.nilsson@...s.com>,
	Andrew Halaney <ahalaney@...hat.com>,
	Choong Yong Liang <yong.liang.choong@...ux.intel.com>,
	Kunihiko Hayashi <hayashi.kunihiko@...ionext.com>,
	Vinicius Costa Gomes <vinicius.gomes@...el.com>,
	intel-wired-lan@...ts.osuosl.org, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	linux-stm32@...md-mailman.stormreply.com,
	linux-arm-kernel@...ts.infradead.org, bpf@...r.kernel.org
Subject: Re: [PATCH iwl-next v5 9/9] igc: Block setting preemptible traffic
 class in taprio

On Wed, Feb 19, 2025 at 09:53:49PM -0500, Faizal Rahim wrote:
> Since preemptible tc implementation is not ready yet, block it from being
> set in taprio. The existing code already blocks it in mqprio.
> 
> Signed-off-by: Faizal Rahim <faizal.abdul.rahim@...ux.intel.com>
> ---
>  drivers/net/ethernet/intel/igc/igc_main.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/drivers/net/ethernet/intel/igc/igc_main.c b/drivers/net/ethernet/intel/igc/igc_main.c
> index 5a6648a12a53..e6a398dbf09b 100644
> --- a/drivers/net/ethernet/intel/igc/igc_main.c
> +++ b/drivers/net/ethernet/intel/igc/igc_main.c
> @@ -6408,6 +6408,10 @@ static int igc_save_qbv_schedule(struct igc_adapter *adapter,
>  	if (!validate_schedule(adapter, qopt))
>  		return -EINVAL;
>  
> +	/* preemptible isn't supported yet */
> +	if (qopt->mqprio.preemptible_tcs)
> +		return -EOPNOTSUPP;
> +
>  	igc_ptp_read(adapter, &now);
>  
>  	if (igc_tsn_is_taprio_activated_by_user(adapter) &&
> -- 
> 2.34.1
>

This patch should be before the patch that makes ethtool_dev_mm_supported()
return true for igc, i.e. 7/9 "igc: Add support to get MAC Merge data via ethtool".
You don't want the kernel to be in a state at all where it accepts a
configuration it doesn't support, even if it's temporary and you're
fixing it up within the same patch set, because it may be visible during
e.g. a git bisect.