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    SubjectRe: [PATCH net-next 02/12] net: dsa: add Renesas RZ/N1 switch tag driver
    Le Thu, 14 Apr 2022 17:22:42 +0300,
    Vladimir Oltean <olteanv@gmail.com> a écrit :

    > > +
    > > +/* To define the outgoing port and to discover the incoming port a TAG is
    > > + * inserted after Src MAC :
    > > + *
    > > + * Dest MAC Src MAC TAG Type
    > > + * ...| 1 2 3 4 5 6 | 1 2 3 4 5 6 | 1 2 3 4 5 6 7 8 | 1 2 |...
    > > + * |<--------------->|
    > > + *
    > > + * See struct a5psw_tag for layout
    > > + */
    > > +
    > > +#define A5PSW_TAG_VALUE 0xE001
    > > +#define A5PSW_TAG_LEN 8
    > > +#define A5PSW_CTRL_DATA_FORCE_FORWARD BIT(0)
    > > +/* This is both used for xmit tag and rcv tagging */
    > > +#define A5PSW_CTRL_DATA_PORT GENMASK(3, 0)
    > > +
    > > +struct a5psw_tag {
    >
    > This needs to be packed.
    >
    > > + u16 ctrl_tag;
    > > + u16 ctrl_data;
    >
    > These need to be __be16.
    >
    > > + u32 ctrl_data2;
    >
    > This needs to be __be32.

    Acked.

    >
    > > +};
    > > +
    > > +static struct sk_buff *a5psw_tag_xmit(struct sk_buff *skb, struct net_device *dev)
    > > +{
    > > + struct a5psw_tag *ptag, tag = {0};
    > > + struct dsa_port *dp = dsa_slave_to_port(dev);
    >
    > Please keep variable declarations sorted in decreasing order of line
    > length (applies throughout the patch series, I won't repeat this comment).

    Acked, both PCS and DSA driver are ok with that rule. Missed that one
    though.
    >
    > > + u32 data2_val;
    > > +
    > > + /* The Ethernet switch we are interfaced with needs packets to be at
    > > + * least 64 bytes (including FCS) otherwise they will be discarded when
    > > + * they enter the switch port logic. When tagging is enabled, we need
    > > + * to make sure that packets are at least 68 bytes (including FCS and
    > > + * tag).
    > > + */
    > > + if (__skb_put_padto(skb, ETH_ZLEN + sizeof(tag), false))
    > > + return NULL;
    > > +
    > > + /* provide 'A5PSW_TAG_LEN' bytes additional space */
    > > + skb_push(skb, A5PSW_TAG_LEN);
    > > +
    > > + /* make room between MACs and Ether-Type to insert tag */
    > > + dsa_alloc_etype_header(skb, A5PSW_TAG_LEN);
    > > +
    > > + ptag = dsa_etype_header_pos_tx(skb);
    > > +
    > > + data2_val = FIELD_PREP(A5PSW_CTRL_DATA_PORT, BIT(dp->index));
    > > + tag.ctrl_tag = htons(A5PSW_TAG_VALUE);
    > > + tag.ctrl_data = htons(A5PSW_CTRL_DATA_FORCE_FORWARD);
    > > + tag.ctrl_data2 = htonl(data2_val);
    > > +
    > > + memcpy(ptag, &tag, sizeof(struct a5psw_tag));
    >
    > sizeof(tag), to be consistent with the other use of sizeof() above?
    > Although, hmm, I think you could get away with editing "ptag" in place.

    I was not sure of the alignment guarantee I would have here. If the
    VLAN header is guaranteed to be aligned on 2 bytes, then I guess it's
    ok to do that in-place.


    --
    Clément Léger,
    Embedded Linux and Kernel engineer at Bootlin
    https://bootlin.com

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