netdev - Re: [PATCHv4 2/2] tg3: Allow ethtool to enable/disable loopback.

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Date:	Thu, 5 May 2011 08:59:28 +0200
From:	Michał Mirosław <mirqus@...il.com>
To:	Mahesh Bandewar <maheshb@...gle.com>
Cc:	Matt Carlson <mcarlson@...adcom.com>,
	David Miller <davem@...emloft.net>,
	netdev <netdev@...r.kernel.org>,
	Michael Chan <mchan@...adcom.com>,
	Tom Herbert <therbert@...gle.com>
Subject: Re: [PATCHv4 2/2] tg3: Allow ethtool to enable/disable loopback.

2011/5/5 Mahesh Bandewar <maheshb@...gle.com>:
> This patch adds tg3_set_features() to handle loopback mode. Currently the
> capability is added for the devices which support internal MAC loopback mode.
> So when enabled, it enables internal-MAC loopback.
>
> Signed-off-by: Mahesh Bandewar <maheshb@...gle.com>
> ---
> Changes since v3:
>  (a) Corrected the condition (|| => &&) where loopback capability is added.
>  (b) set_features() always returns 0.
>  (c) Clear the loopback bit in ndo_open callback to avoid discrepancy.
>
> Changes since v2:
>  Implemtned Joe Perches's style change.
>
> Changes since v1:
>  Implemented Matt Carlson's suggestions.
>  (a) Enable this capability on the devices which are capable of MAC-loopback
>      mode.
>  (b) check if the device is running before making changes.
>  (c) check bits before making changes.
>
>  drivers/net/tg3.c |   69 +++++++++++++++++++++++++++++++++++++++++++++++++++++
>  1 files changed, 69 insertions(+), 0 deletions(-)
>
> diff --git a/drivers/net/tg3.c b/drivers/net/tg3.c
> index 7c7c9a8..7f7a290 100644
> --- a/drivers/net/tg3.c
> +++ b/drivers/net/tg3.c
> @@ -6309,6 +6309,44 @@ dma_error:
>        return NETDEV_TX_OK;
>  }
>
> +static int tg3_set_loopback(struct net_device *dev, u32 features)
> +{
> +       struct tg3 *tp = netdev_priv(dev);
> +       u32 cur_mode = 0;
> +       int retval = 0;

void? You always return zero and don't check it in callers.

[...]
> @@ -9485,6 +9533,15 @@ static int tg3_open(struct net_device *dev)
>
>        netif_tx_start_all_queues(dev);
>
> +       /*
> +        * Reset loopback feature if it was turned on while the device was down
> +        * to avoid and any discrepancy in features reporting.
> +        */
> +       if (dev->features & NETIF_F_LOOPBACK) {
> +               dev->features &= ~NETIF_F_LOOPBACK;
> +               dev->wanted_features &= ~NETIF_F_LOOPBACK;
> +       }
> +

if (dev->features & NETIF_F_LOOPBACK)
  tg3_set_loopback(dev, dev->features);

Whatever you do, don't modify wanted_features in drivers.

BTW, similar problems (also like in previous versions) are in
forcedeth implementation.

Best Regards,
Michał Mirosław
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