linux-kernel - Re: [PATCH net-next v2 2/2] octeon_ep: get max rx packet length from firmware

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Date:   Fri, 24 Nov 2023 17:08:04 +0000
From:   Simon Horman <horms@...nel.org>
To:     Shinas Rasheed <srasheed@...vell.com>
Cc:     netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        hgani@...vell.com, vimleshk@...vell.com, egallen@...hat.com,
        mschmidt@...hat.com, pabeni@...hat.com, kuba@...nel.org,
        davem@...emloft.net, wizhao@...hat.com, konguyen@...hat.com,
        jesse.brandeburg@...el.com, sumang@...vell.com,
        Veerasenareddy Burru <vburru@...vell.com>,
        Sathesh Edara <sedara@...vell.com>,
        Eric Dumazet <edumazet@...gle.com>
Subject: Re: [PATCH net-next v2 2/2] octeon_ep: get max rx packet length from
 firmware

On Wed, Nov 22, 2023 at 10:34:35AM -0800, Shinas Rasheed wrote:
> Max receive packet length can vary across SoCs, so
> this needs to be queried from respective firmware and
> filled by driver. A control net get mtu api should be
> implemented to do the same.
> 
> Signed-off-by: Shinas Rasheed <srasheed@...vell.com>

...

> diff --git a/drivers/net/ethernet/marvell/octeon_ep/octep_main.c b/drivers/net/ethernet/marvell/octeon_ep/octep_main.c
> index 2da00a701df2..423eec5ff3ad 100644
> --- a/drivers/net/ethernet/marvell/octeon_ep/octep_main.c
> +++ b/drivers/net/ethernet/marvell/octeon_ep/octep_main.c
> @@ -1307,6 +1307,7 @@ static int octep_probe(struct pci_dev *pdev, const struct pci_device_id *ent)
>  {
>  	struct octep_device *octep_dev = NULL;
>  	struct net_device *netdev;
> +	int max_rx_pktlen;
>  	int err;
>  
>  	err = pci_enable_device(pdev);
> @@ -1377,8 +1378,15 @@ static int octep_probe(struct pci_dev *pdev, const struct pci_device_id *ent)
>  
>  	netdev->hw_features = NETIF_F_SG;
>  	netdev->features |= netdev->hw_features;
> +
> +	max_rx_pktlen = octep_ctrl_net_get_mtu(octep_dev, OCTEP_CTRL_NET_INVALID_VFID);
> +	if (max_rx_pktlen < 0) {
> +		dev_err(&octep_dev->pdev->dev,
> +			"Failed to get max receive packet size; err = %d\n", max_rx_pktlen);
> +		goto register_dev_err;

Hi Shinas,

This jump will cause this function to return err.  But err is 0 here.
Perhaps it should be set to a negative error value instead?

> +	}
>  	netdev->min_mtu = OCTEP_MIN_MTU;
> -	netdev->max_mtu = OCTEP_MAX_MTU;
> +	netdev->max_mtu = max_rx_pktlen - (ETH_HLEN + ETH_FCS_LEN);
>  	netdev->mtu = OCTEP_DEFAULT_MTU;
>  
>  	err = octep_ctrl_net_get_mac_addr(octep_dev, OCTEP_CTRL_NET_INVALID_VFID,
> -- 
> 2.25.1
>