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    SubjectRe: [PATCH net-next v3 7/7] net: lan966x: Add support for XDP_REDIRECT
    Date
    From: Horatiu Vultur <horatiu.vultur@microchip.com>
    Date: Mon, 21 Nov 2022 22:28:50 +0100

    > Extend lan966x XDP support with the action XDP_REDIRECT. This is similar
    > with the XDP_TX, so a lot of functionality can be reused.
    >
    > Signed-off-by: Horatiu Vultur <horatiu.vultur@microchip.com>
    > ---
    > .../ethernet/microchip/lan966x/lan966x_fdma.c | 83 +++++++++++++++----
    > .../ethernet/microchip/lan966x/lan966x_main.c | 1 +
    > .../ethernet/microchip/lan966x/lan966x_main.h | 10 ++-
    > .../ethernet/microchip/lan966x/lan966x_xdp.c | 31 ++++++-
    > 4 files changed, 109 insertions(+), 16 deletions(-)

    [...]

    > @@ -558,6 +575,10 @@ static int lan966x_fdma_napi_poll(struct napi_struct *napi, int weight)
    > case FDMA_TX:
    > lan966x_fdma_rx_advance_dcb(rx);
    > continue;
    > + case FDMA_REDIRECT:
    > + lan966x_fdma_rx_advance_dcb(rx);
    > + redirect = true;
    > + continue;

    I think you can save a couple lines here and avoid small code dup:

    + case FDMA_REDIRECT:
    + redirect = true;
    + fallthrough;
    case FDMA_TX:
    lan966x_fdma_rx_advance_dcb(rx);
    continue;

    The logics stays the same.

    > case FDMA_DROP:
    > lan966x_fdma_rx_free_page(rx);
    > lan966x_fdma_rx_advance_dcb(rx);

    [...]

    > @@ -178,6 +180,7 @@ struct lan966x_tx_dcb_buf {
    > struct net_device *dev;
    > struct sk_buff *skb;
    > struct xdp_frame *xdpf;
    > + bool xdp_ndo;

    I suggest carefully inspecting this struct with pahole (or by just
    printkaying its layout/sizes/offsets at runtime) and see if there's
    any holes and how it could be optimized.
    Also, it's just my personal preference, but it's not that unpopular:
    I don't trust bools inside structures as they may surprise with
    their sizes or alignment depending on the architercture. Considering
    all the blah I wrote, I'd define it as:

    struct lan966x_tx_dcb_buf {
    dma_addr_t dma_addr; // can be 8 bytes on 32-bit plat
    struct net_device *dev; // ensure natural alignment
    struct sk_buff *skb;
    struct xdp_frame *xdpf;
    u32 len;
    u32 xdp_ndo:1; // put all your booleans here in
    u32 used:1; // one u32
    ...
    };

    BTW, we usually do union { skb, xdpf } since they're mutually
    exclusive. And to distinguish between XDP and regular Tx you can use
    one more bit/bool. This can also come handy later when you add XSk
    support (you will be adding it, right? Please :P).

    > int len;
    > dma_addr_t dma_addr;
    > bool used;

    [...]

    > --
    > 2.38.0

    Thanks,
    Olek

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