netdev - RE: [PATCH] r8152: limit MAC pass-through to one device

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Date:   Wed, 10 Oct 2018 17:18:17 +0000
From:   <Mario.Limonciello@...l.com>
To:     <oneukum@...e.com>, <netdev@...r.kernel.org>,
        <davem@...emloft.net>, <jkohoutek@...e.com>
Subject: RE: [PATCH] r8152: limit MAC pass-through to one device

> 
> MAC address having to be unique, a MAC coming from the host
> must be used at most once at a time. Hence the users must
> be recorded and additional users must fall back to conventional
> methods.

I checked with the internal team and actually applies pass through MAC on both
Windows Realtek driver and in UEFI network stack this applies to ALL supported
Realtek devices (R8153-AD).

> 
> Signed-off-by: Oliver Neukum <oneukum@...e.com>
> Fixes: 34ee32c9a5696 ("r8152: Add support for setting pass through MAC address on
> RTL8153-AD")
> ---
>  drivers/net/usb/r8152.c | 14 +++++++++++++-
>  1 file changed, 13 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/net/usb/r8152.c b/drivers/net/usb/r8152.c
> index f1b5201cc320..7345a2258ee4 100644
> --- a/drivers/net/usb/r8152.c
> +++ b/drivers/net/usb/r8152.c
> @@ -766,6 +766,9 @@ enum tx_csum_stat {
>  	TX_CSUM_NONE
>  };
> 
> +/* pass through MACs are per host, hence concurrent use is forbidden */
> +static struct r8152 *pass_through_user = NULL;
> +
>  /* Maximum number of multicast addresses to filter (vs. Rx-all-multicast).
>   * The RTL chips use a 64 element hash table based on the Ethernet CRC.
>   */
> @@ -1221,7 +1224,14 @@ static int set_ethernet_addr(struct r8152 *tp)
>  		 * or system doesn't provide valid _SB.AMAC this will be
>  		 * be expected to non-zero
>  		 */
> -		ret = vendor_mac_passthru_addr_read(tp, &sa);
> +		if (!pass_through_user) {
> +			ret = vendor_mac_passthru_addr_read(tp, &sa);
> +			if (ret >= 0)
> +				/* we must record the user against concurrent use
> */
> +				pass_through_user = tp;
> +		} else {
> +			ret = -EBUSY;
> +		}
>  		if (ret < 0)
>  			ret = pla_ocp_read(tp, PLA_BACKUP, 8, sa.sa_data);
>  	}
> @@ -5304,6 +5314,8 @@ static void rtl8152_disconnect(struct usb_interface *intf)
>  		cancel_delayed_work_sync(&tp->hw_phy_work);
>  		tp->rtl_ops.unload(tp);
>  		free_netdev(tp->netdev);
> +		if (pass_through_user == tp)
> +			pass_through_user = NULL;
>  	}
>  }
> 
> --
> 2.16.4