[PATCH] net: ftmac100: set max_mtu to allow DSA overhead setting

[PATCH] net: ftmac100: set max_mtu to allow DSA overhead setting

[Sergei Antonov]

In case ftmac100 is used with a DSA switch, Linux wants to set MTU
to 1504 to accommodate for DSA overhead. With the default max_mtu
it leads to the error message:
 ftmac100 92000000.mac eth0: error -22 setting MTU to 1504 to include DSA overhead

ftmac100 supports packet length 1518 (MAX_PKT_SIZE constant), so it is
safe to report it in max_mtu.

Signed-off-by: Sergei Antonov <saproj@gmail.com>
---
 drivers/net/ethernet/faraday/ftmac100.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/net/ethernet/faraday/ftmac100.c b/drivers/net/ethernet/faraday/ftmac100.c
index 8a341e2d5833..2e6524009b19 100644
--- a/drivers/net/ethernet/faraday/ftmac100.c
+++ b/drivers/net/ethernet/faraday/ftmac100.c
@@ -1075,6 +1075,7 @@ static int ftmac100_probe(struct platform_device *pdev)
 	SET_NETDEV_DEV(netdev, &pdev->dev);
 	netdev->ethtool_ops = &ftmac100_ethtool_ops;
 	netdev->netdev_ops = &ftmac100_netdev_ops;
+	netdev->max_mtu = MAX_PKT_SIZE;
 
 	platform_set_drvdata(pdev, netdev);
 
-- 
2.34.1

Re: [PATCH] net: ftmac100: set max_mtu to allow DSA overhead setting

[Andrew Lunn]

On Sun, Aug 21, 2022 at 07:08:44PM +0300, Sergei Antonov wrote:
> In case ftmac100 is used with a DSA switch, Linux wants to set MTU
> to 1504 to accommodate for DSA overhead. With the default max_mtu
> it leads to the error message:
>  ftmac100 92000000.mac eth0: error -22 setting MTU to 1504 to include DSA overhead
> 
> ftmac100 supports packet length 1518 (MAX_PKT_SIZE constant), so it is
> safe to report it in max_mtu.
> 
> Signed-off-by: Sergei Antonov <saproj@gmail.com>

Reviewed-by: Andrew Lunn <andrew@lunn.ch>

    Andrew

Re: [PATCH] net: ftmac100: set max_mtu to allow DSA overhead setting

[patchwork-bot+netdevbpf]

Hello:

This patch was applied to netdev/net-next.git (master)
by Jakub Kicinski <kuba@kernel.org>:

On Sun, 21 Aug 2022 19:08:44 +0300 you wrote:
> In case ftmac100 is used with a DSA switch, Linux wants to set MTU
> to 1504 to accommodate for DSA overhead. With the default max_mtu
> it leads to the error message:
>  ftmac100 92000000.mac eth0: error -22 setting MTU to 1504 to include DSA overhead
> 
> ftmac100 supports packet length 1518 (MAX_PKT_SIZE constant), so it is
> safe to report it in max_mtu.
> 
> [...]

Here is the summary with links:
  - net: ftmac100: set max_mtu to allow DSA overhead setting
    https://git.kernel.org/netdev/net-next/c/6c2c782fa013

You are awesome, thank you!
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