linux-kernel - Re: [PATCH][next] net: systemport: fix double shift of a vlan_tci by VLAN_PRIO

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Message-ID: <3e581bfd-7447-881f-1e0b-9ab1ccd4496d@gmail.com>
Date:   Wed, 8 Jul 2020 13:32:38 -0700
From:   Florian Fainelli <f.fainelli@...il.com>
To:     Colin King <colin.king@...onical.com>,
        "David S . Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        bcm-kernel-feedback-list@...adcom.com, netdev@...r.kernel.org
Cc:     kernel-janitors@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH][next] net: systemport: fix double shift of a vlan_tci by
 VLAN_PRIO_SHIFT



On 7/8/2020 11:37 AM, Colin King wrote:
> From: Colin Ian King <colin.king@...onical.com>
> 
> Currently the u16 skb->vlan_tci is being right  shifted twice by
> VLAN_PRIO_SHIFT, once in the macro skb_vlan_tag_get_pri and explicitly
> by VLAN_PRIO_SHIFT afterwards. The combined shift amount is larger than
> the u16 so the end result is always zero.  Remove the second explicit
> shift as this is extraneous.
> 
> Fixes: 6e9fdb60d362 ("net: systemport: Add support for VLAN transmit acceleration")
> Addresses-Coverity: ("Operands don't affect result")
> Signed-off-by: Colin Ian King <colin.king@...onical.com>

Acked-by: Florian Fainelli <f.fainelli@...il.com>

The change was forward ported from a 4.9 kernel where the shift is not
done, I should have checked the helper usage, thanks!
-- 
Florian