netdev - Re: [PATCH net] net: amd-xgbe: use EOPNOTSUPP instead of ENOTSUPP in xgbe_phy_mii_read

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Message-ID: <aO4x_fD_g3nMjYnZ@horms.kernel.org>
Date: Tue, 14 Oct 2025 12:20:29 +0100
From: Simon Horman <horms@...nel.org>
To: Alok Tiwari <alok.a.tiwari@...cle.com>
Cc: Shyam-sundar.S-k@....com, kuba@...nel.org, andrew+netdev@...n.ch,
	davem@...emloft.net, edumazet@...gle.com, pabeni@...hat.com,
	linux@...linux.org.uk, netdev@...r.kernel.org
Subject: Re: [PATCH net] net: amd-xgbe: use EOPNOTSUPP instead of ENOTSUPP in
 xgbe_phy_mii_read_c45

On Mon, Oct 13, 2025 at 10:19:28AM -0700, Alok Tiwari wrote:
> The MDIO read callback xgbe_phy_mii_read_c45() can propagate its return
> value up through phylink_mii_ioctl() to user space via netdev ioctls such
> as SIOCGMIIREG. Returning ENOTSUPP results in user space seeing
> "Unknown error", since ENOTSUPP is not a standard errno value.
> 
> Replace ENOTSUPP with EOPNOTSUPP to align with the MDIO core’s
> usage and ensure user space receives a proper "Operation not supported"
> error instead of an unknown code.
> 
> Fixes: 070f6186a2f1 ("amd-xgbe: Separate C22 and C45 transactions")
> Signed-off-by: Alok Tiwari <alok.a.tiwari@...cle.com>

Hi Alok,

I lean somewhat towards this being an enhancement rather than a fix.
But if we want to go down the fixes road, then I think the problem
was introduced in the implementation of xgbe_phy_mii_read() in
commit abf0a1c2b26a ("amd-xgbe: Add support for SFP+ modules").
Although I do see how you could argue for the commit you have cited.

The above aside, this patch looks good to me.

Reviewed-by: Simon Horman <horms@...nel.org>

...