From bcccb0a535bb99616e4b992568371efab1ab14e8 Mon Sep 17 00:00:00 2001 From: Vladimir Oltean Date: Sun, 25 Aug 2019 21:32:12 +0300 Subject: [PATCH] net: dsa: tag_8021q: Future-proof the reserved fields in the custom VID After witnessing the discussion in https://lkml.org/lkml/2019/8/14/151 w.r.t. ioctl extensibility, it became clear that such an issue might prevent that the 3 RSV bits inside the DSA 802.1Q tag might also suffer the same fate and be useless for further extension. So clearly specify that the reserved bits should currently be transmitted as zero and ignored on receive. The DSA tagger already does this (and has always did), and is the only known user so far (no Wireshark dissection plugin, etc). So there should be no incompatibility to speak of. Fixes: 0471dd429cea ("net: dsa: tag_8021q: Create a stable binary format") Signed-off-by: Vladimir Oltean Reviewed-by: Florian Fainelli Signed-off-by: David S. Miller --- net/dsa/tag_8021q.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/net/dsa/tag_8021q.c b/net/dsa/tag_8021q.c index 6ebbd799c4eb..67a1bc635a7b 100644 --- a/net/dsa/tag_8021q.c +++ b/net/dsa/tag_8021q.c @@ -28,6 +28,7 @@ * * RSV - VID[9]: * To be used for further expansion of SWITCH_ID or for other purposes. + * Must be transmitted as zero and ignored on receive. * * SWITCH_ID - VID[8:6]: * Index of switch within DSA tree. Must be between 0 and @@ -35,6 +36,7 @@ * * RSV - VID[5:4]: * To be used for further expansion of PORT or for other purposes. + * Must be transmitted as zero and ignored on receive. * * PORT - VID[3:0]: * Index of switch port. Must be between 0 and DSA_MAX_PORTS - 1. -- 2.30.2