[<prev] [next>] [<thread-prev] [day] [month] [year] [list]
Message-ID: <Y/XYpLz6K78T2elz@gmail.com>
Date: Wed, 22 Feb 2023 08:56:04 +0000
From: Martin Habets <habetsm.xilinx@...il.com>
To: Edward Cree <ecree.xilinx@...il.com>
Cc: Leon Romanovsky <leon@...nel.org>, edward.cree@....com,
linux-net-drivers@....com, davem@...emloft.net, kuba@...nel.org,
pabeni@...hat.com, edumazet@...gle.com, netdev@...r.kernel.org
Subject: Re: [PATCH net-next] sfc: support offloading TC VLAN push/pop
actions to the MAE
On Tue, Feb 21, 2023 at 08:32:13PM +0000, Edward Cree wrote:
> On 19/02/2023 09:21, Leon Romanovsky wrote:
> > On Thu, Feb 16, 2023 at 04:04:42PM +0000, edward.cree@....com wrote:
> >> From: Edward Cree <ecree.xilinx@...il.com>
> >>
> >> EF100 can pop and/or push up to two VLAN tags.
> >>
> >> Signed-off-by: Edward Cree <ecree.xilinx@...il.com>
> ...
> >> + /* Translate vlan actions from bitmask to count */
> >> + switch (act->vlan_push) {
> >> + case 0:
> >> + case 1:
> >> + vlan_push = act->vlan_push;
> >> + break;
> >> + case 2: /* can't happen */
> >
> > There is no need in case here as "default" will catch.
> >
> >> + default:
> >> + return -EINVAL;
> >> + case 3:
> >> + vlan_push = 2;
> >> + break;
> >> + }
> >> + switch (act->vlan_pop) {
> >> + case 0:
> >> + case 1:
> >> + vlan_pop = act->vlan_pop;
> >> + break;
> >> + case 2: /* can't happen */
> >> + default:
> >> + return -EINVAL;
> >
> > Please rely switch-case semantics and don't put default in the middle.
>
> It's legal C and as far as I can tell there's nothing in coding-style.rst
> about it; I did it this way so as to put the cases in the logical(?)
> ascending order and try to make the code self-document the possible
> values of the act-> fields.
> Arguably it's the 'default:' rather than the 'case 2:' that's unnecessary
> as the switch argument is an unsigned:2 bitfield, so it can only take on
> these four values.
Can you replace the switch statement with
vlan_push = act->vlan_push & 1 + act->vlan_push & 2;
Even then it would seem prudent to guard against act->vlan_push == 2.
Martin
> Although on revisiting this code I wonder if it makes more sense just to
> use the 'count' (rather than 'bitmask') form throughout, including in
> act->vlan_push/pop; it makes the tc.c side of the code slightly more
> involved, but gets rid of this translation entirely. WDYT?
>
> -ed
Powered by blists - more mailing lists