Re: [PATCH 3/3] gianfar: fix endianness for hardware timestamp

[Richard Cochran]

On Mon, Feb 22, 2016 at 02:49:33PM +0800, Yangbo Lu wrote:
> @@ -2708,6 +2708,7 @@ static void gfar_clean_tx_ring(struct gfar_priv_tx_q 
> *tx_queue)
>                       struct skb_shared_hwtstamps shhwtstamps;
>                       u64 *ns = (u64 *)(((uintptr_t)skb->data + 0x10) &
>                                         ~0x7UL);
> +                     *ns = be64_to_cpu(*ns);
>  
>                       memset(&shhwtstamps, 0, sizeof(shhwtstamps));
>                       shhwtstamps.hwtstamp = ns_to_ktime(*ns);

There is no point in modifying the buffer data in place.

Instead, do this:

                        memset(&shhwtstamps, 0, sizeof(shhwtstamps));
                        shhwtstamps.hwtstamp = ns_to_ktime(be64_to_cpu(*ns));

or this:

                        u64 ns, *ptr = (u64 *)(((uintptr_t)skb->data + 0x10) &
                                               ~0x7UL);
                        ns = be64_to_cpu(*ptr);

                        memset(&shhwtstamps, 0, sizeof(shhwtstamps));
                        shhwtstamps.hwtstamp = ns_to_ktime(ns);

> @@ -3037,6 +3038,7 @@ static void gfar_process_frame(struct net_device *ndev, 
> struct sk_buff *skb)
>       if (priv->hwts_rx_en) {
>               struct skb_shared_hwtstamps *shhwtstamps = skb_hwtstamps(skb);
>               u64 *ns = (u64 *) skb->data;
> +             *ns = be64_to_cpu(*ns);
>  
>               memset(shhwtstamps, 0, sizeof(*shhwtstamps));
>               shhwtstamps->hwtstamp = ns_to_ktime(*ns);

Same here.

Thanks,
Richard