linux-kernel - [RFC PATCH net] net: taprio: Validate offload support using NETIF_F_HW_TC in hw

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Message-ID: <20250729061034.3400624-1-vineeth.karumanchi@amd.com>
Date: Tue, 29 Jul 2025 11:40:34 +0530
From: Vineeth Karumanchi <vineeth.karumanchi@....com>
To: <git@....com>, <vinicius.gomes@...el.com>, <jhs@...atatu.com>,
	<xiyou.wangcong@...il.com>, <jiri@...nulli.us>, <davem@...emloft.net>,
	<edumazet@...gle.com>, <kuba@...nel.org>, <pabeni@...hat.com>,
	<horms@...nel.org>, <netdev@...r.kernel.org>, <linux-kernel@...r.kernel.org>
CC: <vineeth.karumanchi@....com>
Subject: [RFC PATCH net] net: taprio: Validate offload support using NETIF_F_HW_TC in hw_features

The current taprio offload validation relies solely on the presence of
.ndo_setup_tc, which is insufficient. Some IP versions of a driver expose
.ndo_setup_tc but lack actual hardware offload support for taprio.

To address this, add a check for NETIF_F_HW_TC in netdev->hw_features.
This ensures that taprio offload is only enabled on devices that
explicitly advertise hardware traffic control capabilities.

Note: Some drivers already set NETIF_F_HW_TC alongside .ndo_setup_tc.
Follow-up patches will be submitted to update remaining drivers if this
approach is accepted.

Signed-off-by: Vineeth Karumanchi <vineeth.karumanchi@....com>
---
 net/sched/sch_taprio.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/sched/sch_taprio.c b/net/sched/sch_taprio.c
index 2b14c81a87e5..a797995bdc8d 100644
--- a/net/sched/sch_taprio.c
+++ b/net/sched/sch_taprio.c
@@ -1506,7 +1506,7 @@ static int taprio_enable_offload(struct net_device *dev,
 	struct tc_taprio_caps caps;
 	int tc, err = 0;

-	if (!ops->ndo_setup_tc) {
+	if (!ops->ndo_setup_tc || !(dev->hw_features & NETIF_F_HW_TC)) {
 		NL_SET_ERR_MSG(extack,
 			       "Device does not support taprio offload");
 		return -EOPNOTSUPP;
-- 
2.34.1