netdev - Re: [PATCHv2 2/3] usbnet: add method for reporting speed without MDIO

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Date:   Fri, 22 Jan 2021 02:56:57 +0000
From:   Grant Grundler <grundler@...omium.org>
To:     Oliver Neukum <oneukum@...e.com>
Cc:     Hayes Wang <hayeswang@...ltek.com>,
        Grant Grundler <grundler@...omium.org>,
        David Miller <davem@...emloft.net>,
        netdev <netdev@...r.kernel.org>, linux-usb@...r.kernel.org,
        Roland Dreier <roland@...nel.org>
Subject: Re: [PATCHv2 2/3] usbnet: add method for reporting speed without MDIO

On Thu, Jan 21, 2021 at 12:57 PM Oliver Neukum <oneukum@...e.com> wrote:
>
> The old method for reporting network speed upwards
> assumed that a device uses MDIO and uses the generic phy
> functions based on that.
> Add a a primitive internal version not making the assumption
> reporting back directly what the status operations record.
>
> v2: adjusted to recent changes
>
> Signed-off-by: Oliver Neukum <oneukum@...e.com>
> Tested-by: Roland Dreier <roland@...nel.org>
> ---
>  drivers/net/usb/usbnet.c   | 23 +++++++++++++++++++++++
>  include/linux/usb/usbnet.h |  4 ++++
>  2 files changed, 27 insertions(+)
>
> diff --git a/drivers/net/usb/usbnet.c b/drivers/net/usb/usbnet.c
> index e2ca88259b05..6f8fcc276ca7 100644
> --- a/drivers/net/usb/usbnet.c
> +++ b/drivers/net/usb/usbnet.c
> @@ -961,6 +961,27 @@ int usbnet_get_link_ksettings_mdio(struct net_device *net,
>  }
>  EXPORT_SYMBOL_GPL(usbnet_get_link_ksettings_mdio);
>
> +int usbnet_get_link_ksettings_internal(struct net_device *net,
> +                                       struct ethtool_link_ksettings *cmd)
> +{
> +       struct usbnet *dev = netdev_priv(net);
> +
> +       /* the assumption that speed is equal on tx and rx
> +        * is deeply engrained into the networking layer.

Another nit: s/engrained/ingrained

Also, the word "symmetric" is more commonly used to describe when RX
speed == TX speed (vs "equal").

cheers,
grant

> +        * For wireless stuff it is not true.
> +        * We assume that rxspeed matters more.
> +        */
> +       if (dev->rxspeed != SPEED_UNKNOWN)
> +               cmd->base.speed = dev->rxspeed / 1000000;
> +       else if (dev->txspeed != SPEED_UNKNOWN)
> +               cmd->base.speed = dev->txspeed / 1000000;
> +       else
> +               cmd->base.speed = SPEED_UNKNOWN;
> +
> +       return 0;
> +}
> +EXPORT_SYMBOL_GPL(usbnet_get_link_ksettings_internal);
> +
>  int usbnet_set_link_ksettings_mdio(struct net_device *net,
>                               const struct ethtool_link_ksettings *cmd)
>  {
> @@ -1664,6 +1685,8 @@ usbnet_probe (struct usb_interface *udev, const struct usb_device_id *prod)
>         dev->intf = udev;
>         dev->driver_info = info;
>         dev->driver_name = name;
> +       dev->rxspeed = SPEED_UNKNOWN; /* unknown or handled by MII */
> +       dev->txspeed = SPEED_UNKNOWN;
>
>         net->tstats = netdev_alloc_pcpu_stats(struct pcpu_sw_netstats);
>         if (!net->tstats)
> diff --git a/include/linux/usb/usbnet.h b/include/linux/usb/usbnet.h
> index fd65b7a5ee15..a91c6defb104 100644
> --- a/include/linux/usb/usbnet.h
> +++ b/include/linux/usb/usbnet.h
> @@ -53,6 +53,8 @@ struct usbnet {
>         u32                     hard_mtu;       /* count any extra framing */
>         size_t                  rx_urb_size;    /* size for rx urbs */
>         struct mii_if_info      mii;
> +       long                    rxspeed;        /* if MII is not used */
> +       long                    txspeed;        /* if MII is not used */
>
>         /* various kinds of pending driver work */
>         struct sk_buff_head     rxq;
> @@ -269,6 +271,8 @@ extern void usbnet_purge_paused_rxq(struct usbnet *);
>
>  extern int usbnet_get_link_ksettings_mdio(struct net_device *net,
>                                      struct ethtool_link_ksettings *cmd);
> +extern int usbnet_get_link_ksettings_internal(struct net_device *net,
> +                                       struct ethtool_link_ksettings *cmd);
>  extern int usbnet_set_link_ksettings_mdio(struct net_device *net,
>                                      const struct ethtool_link_ksettings *cmd);
>  extern u32 usbnet_get_link(struct net_device *net);
> --
> 2.26.2
>