Re: [PATCH net-next v3 3/7] net: lan966x: Add len field to lan966x_tx_dcb_buf

Horatiu Vultur
2022-11-22T21:17:03Z

The 11/22/2022 12:30, Alexander Lobakin wrote:
>
> From: Horatiu Vultur <horatiu.vultur@microchip.com>
> Date: Mon, 21 Nov 2022 22:28:46 +0100
>
> > Currently when a frame was transmitted, it is required to unamp the
> > frame that was transmitted. The length of the frame was taken from the
> > transmitted skb. In the future we might not have an skb, therefore store
> > the length skb directly in the lan966x_tx_dcb_buf and use this one to
> > unamp the frame.
> >
> > Signed-off-by: Horatiu Vultur <horatiu.vultur@microchip.com>
> > ---
> > drivers/net/ethernet/microchip/lan966x/lan966x_fdma.c | 5 +++--
> > drivers/net/ethernet/microchip/lan966x/lan966x_main.h | 1 +
> > 2 files changed, 4 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/net/ethernet/microchip/lan966x/lan966x_fdma.c b/drivers/net/ethernet/microchip/lan966x/lan966x_fdma.c
> > index 94c720e59caee..384ed34197d58 100644
> > --- a/drivers/net/ethernet/microchip/lan966x/lan966x_fdma.c
> > +++ b/drivers/net/ethernet/microchip/lan966x/lan966x_fdma.c
> > @@ -391,12 +391,12 @@ static void lan966x_fdma_tx_clear_buf(struct lan966x *lan966x, int weight)
> > continue;
> >
> > dcb_buf->dev->stats.tx_packets++;
> > - dcb_buf->dev->stats.tx_bytes += dcb_buf->skb->len;
> > + dcb_buf->dev->stats.tx_bytes += dcb_buf->len;
> >
> > dcb_buf->used = false;
> > dma_unmap_single(lan966x->dev,
> > dcb_buf->dma_addr,
> > - dcb_buf->skb->len,
> > + dcb_buf->len,
> > DMA_TO_DEVICE);
> > if (!dcb_buf->ptp)
> > dev_kfree_skb_any(dcb_buf->skb);
> > @@ -709,6 +709,7 @@ int lan966x_fdma_xmit(struct sk_buff *skb, __be32 *ifh, struct net_device *dev)
> > /* Fill up the buffer */
> > next_dcb_buf = &tx->dcbs_buf[next_to_use];
> > next_dcb_buf->skb = skb;
> > + next_dcb_buf->len = skb->len;
> > next_dcb_buf->dma_addr = dma_addr;
> > next_dcb_buf->used = true;
> > next_dcb_buf->ptp = false;
> > diff --git a/drivers/net/ethernet/microchip/lan966x/lan966x_main.h b/drivers/net/ethernet/microchip/lan966x/lan966x_main.h
> > index bc93051aa0798..7bb9098496f60 100644
> > --- a/drivers/net/ethernet/microchip/lan966x/lan966x_main.h
> > +++ b/drivers/net/ethernet/microchip/lan966x/lan966x_main.h
> > @@ -175,6 +175,7 @@ struct lan966x_rx {
> > struct lan966x_tx_dcb_buf {
> > struct net_device *dev;
> > struct sk_buff *skb;
> > + int len;
>
> Nit: perhaps you can define it as `u32` since fram length can't be
> negative?

The length is always positive. I will update this in the next version.

>
> > dma_addr_t dma_addr;
>
> Oh, also, on platforms with 64-bit addressing, `int len` placed in
> between ::skb and ::dma_addr would create a 4-byte hole in the
> structure. Placing `len` after ::dma_addr would make it holeless on
> any architercture.

Thanks for the suggestion.
I will make sure that lan966x_tx_dcb_buf will not have any holes. In
this patch I will arrange the members and in the next patches where
I will modify the struct, I will add them at the right place.

>
> > bool used;
> > bool ptp;
> > --
> > 2.38.0
>
> Thanks,
> Olek

--
/Horatiu