linux-kernel - Re: [PATCH net] net: phy: mscc: Add error check when __phy

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Message-ID: <YnpZphRYEZJm/9D6@lunn.ch>
Date:   Tue, 10 May 2022 14:25:10 +0200
From:   Andrew Lunn <andrew@...n.ch>
To:     Wan Jiabing <wanjiabing@...o.com>
Cc:     Heiner Kallweit <hkallweit1@...il.com>,
        Russell King <linux@...linux.org.uk>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Antoine Tenart <atenart@...nel.org>, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, kael_w@...h.net
Subject: Re: [PATCH net] net: phy: mscc: Add error check when __phy_read()
 failed

On Tue, May 10, 2022 at 11:54:56AM +0800, Wan Jiabing wrote:
> Calling __phy_read() might return a negative error code. Use 'int'
> to declare variables which call __phy_read() and also add error check
> for them.

It would be good to add a comment here:

The numerous callers of vsc8584_macsec_phy_read() don't expect it to
fail. So don't return the error code from __phy_read(), but also don't
return random values if it does fail.

The commit message should try to answer any questions to reviewer
has. And when i first looked at the change, i thought this is wrong,
the error code is thrown away. But then i remembers our discussion. So
it is good to mention that in the commit message.

> Fixes: fa164e40c53b ("net: phy: mscc: split the driver into separate files")
> Signed-off-by: Wan Jiabing <wanjiabing@...o.com>
> ---
>  drivers/net/phy/mscc/mscc_macsec.c | 11 ++++++++---
>  1 file changed, 8 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/net/phy/mscc/mscc_macsec.c b/drivers/net/phy/mscc/mscc_macsec.c
> index b7b2521c73fb..8a63e32fafa0 100644
> --- a/drivers/net/phy/mscc/mscc_macsec.c
> +++ b/drivers/net/phy/mscc/mscc_macsec.c
> @@ -22,9 +22,9 @@
>  static u32 vsc8584_macsec_phy_read(struct phy_device *phydev,
>  				   enum macsec_bank bank, u32 reg)
>  {
> -	u32 val, val_l = 0, val_h = 0;
>  	unsigned long deadline;
> -	int rc;
> +	int rc, val, val_l, val_h;
> +	u32 ret = 0;

Networking code uses "reverse christmas tree", meaning these lines
should be sorted, longest first, shortest last. So deadline needs to
come after val_h.

     Andrew