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Message-ID: <6346b451.170a0220.2c49b.3ebc@mx.google.com> Date: Wed, 12 Oct 2022 14:34:22 +0200 From: Christian Marangi <ansuelsmth@...il.com> To: Andrew Lunn <andrew@...n.ch> Cc: Vivien Didelot <vivien.didelot@...il.com>, Florian Fainelli <f.fainelli@...il.com>, Vladimir Oltean <olteanv@...il.com>, "David S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>, "Russell King (Oracle)" <rmk+kernel@...linux.org.uk>, netdev@...r.kernel.org, linux-kernel@...r.kernel.org, Pawel Dembicki <paweldembicki@...il.com>, Lech Perczak <lech.perczak@...il.com> Subject: Re: [net PATCH 1/2] net: dsa: qca8k: fix inband mgmt for big-endian systems On Wed, Oct 12, 2022 at 02:29:26PM +0200, Andrew Lunn wrote: > On Mon, Oct 10, 2022 at 02:44:46PM +0200, Christian Marangi wrote: > > On Mon, Oct 10, 2022 at 08:53:01PM +0200, Andrew Lunn wrote: > > > > /* Special struct emulating a Ethernet header */ > > > > struct qca_mgmt_ethhdr { > > > > - u32 command; /* command bit 31:0 */ > > > > - u32 seq; /* seq 63:32 */ > > > > - u32 mdio_data; /* first 4byte mdio */ > > > > + __le32 command; /* command bit 31:0 */ > > > > + __le32 seq; /* seq 63:32 */ > > > > + __le32 mdio_data; /* first 4byte mdio */ > > > > __be16 hdr; /* qca hdr */ > > > > } __packed; > > > > > > It looks odd that hdr is BE while the rest are LE. Did you check this? > > > > > > Andrew > > > > Yes we did many test to analyze this and I just checked with some > > tcpdump that the hdr is BE everytime. > > That might actual make sense. The comment says: > > > > > /* Special struct emulating a Ethernet header */ > > And hdr is where the Ether type would be, which is network endian, > i.e. big endian. > > Andrew Yes that is my theory... hdr is in the ether type position so it's the only part that the switch treat in a standard way as it has to be like that or a dev creating a tagger driver would have no way to understand if the packet is autocast, in band ack or a simple packet so who created the fw for the switch had this concern in mind and stick to keeping at least the hdr in a standard way. -- Ansuel
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