[PATCHv2,2/3] usbnet: add method for reporting speed without MDIO

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@suse.com>
Tested-by: Roland Dreier <roland@kernel.org>
---
 drivers/net/usb/usbnet.c   | 23 +++++++++++++++++++++++
 include/linux/usb/usbnet.h |  4 ++++
 2 files changed, 27 insertions(+)

On Thu, Jan 21, 2021 at 12:57 PM Oliver Neukum <oneukum@suse.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.

Excellent!  I wasted a bunch of time looking at emulating the MDIO
interface and decided that was too hacky.  I didn't realize it could
be so easy to fork off a different method to collect the most recently
reported speed. Thank you!

> v2: adjusted to recent changes
>
> Signed-off-by: Oliver Neukum <oneukum@suse.com>
> Tested-by: Roland Dreier <roland@kernel.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.
> +        * 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;

Nit: Use of SPEED_UNKNOWN here can be confusing since the units for
rxspeed/txspeed are bps, not Mbps (AFAICT SPEED_XXX are Mbps numbers).
In other words, this is the only usbnet location that could use
SPEED_xxx define and other developers might not realize that.
Personally, I'd rather set the fields to zero here.

>
>         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 */

Do you want to note the units used (bps) in the trailing comment?

The numbers for cdc_ncm and cdc_ether will be "bits per second" due to
how older modems could report "odd" (from an ethernet point of view)
speeds.

Also, the changes I just submitted (and kuba@kernel.org accepted)
named these "rx_speed" (with underscore). I don't care which it is but
just wanted to warn about and apologize for the conflict.

cheers,
grant

>         /* 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
>