[PATCH net 1/1] net: ethtool: mm: Allow Verify Enabled before Tx Enabled

[Chwee-Lin Choong]

The current implementation of ethtool --set-mm restricts
enabling the "verify_enabled" flag unless Tx preemption
(tx_enabled) is already enabled. By default, verification
is disabled, and enabling Tx preemption immediately activates
preemption.

When verification is intended, users can only enable verification
after enabling tx_enabled, which temporarily deactivates preemption
until verification completes. This creates an inconsistent and
restrictive workflow.

This patch modifies ethtool --set-mm to allow users to pre-enable
verification locally using ethtool before Tx preemption is enabled
via ethtool or negotiated through LLDP with a link partner.

Current Workflow:
1. Enable pmac_enabled → Preemption supported
2. Enable tx_enabled → Preemption Tx enabled
3. verify_enabled defaults to off → Preemption active
4. Enable verify_enabled → Preemption deactivates → Verification starts
                         → Verification success → Preemption active.

Proposed Workflow:
1. Enable pmac_enabled → Preemption supported
2. Enable verify_enabled → Preemption supported and Verify enabled
3. Enable tx_enabled → Preemption Tx enabled → Verification starts
                     → Verification success → Preemption active.

Fixes: 35b288d6e3d4 ("net: ethtool: mm: sanitize some UAPI configurations")
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Chwee-Lin Choong <chwee.lin.choong@xxxxxxxxx>
Reviewed-by: Choong Yong Liang <yong.liang.choong@xxxxxxxxxxxxxxx>
Reviewed-by: Faizal Rahim <faizal.abdul.rahim@xxxxxxxxxxxxxxx>
---
 net/ethtool/mm.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/net/ethtool/mm.c b/net/ethtool/mm.c
index 2816bb23c3ad..8a66ea3148d1 100644
--- a/net/ethtool/mm.c
+++ b/net/ethtool/mm.c
@@ -214,8 +214,8 @@ static int ethnl_set_mm(struct ethnl_req_info *req_info, struct genl_info *info)
 		return -ERANGE;
 	}
 
-	if (cfg.verify_enabled && !cfg.tx_enabled) {
-		NL_SET_ERR_MSG(extack, "Verification requires TX enabled");
+	if (cfg.verify_enabled && !cfg.pmac_enabled) {
+		NL_SET_ERR_MSG(extack, "Verify enabled requires pMAC enabled");
 		return -EINVAL;
 	}
 
-- 
2.34.1