netdev - Re: [net-next] net: phy: Check for read errors in SIOCGMIIREG

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Message-ID: <CAMuHMdXajVM9=jLMayyC=RziqHz9HLZRcg864qw1NN2txUcKpQ@mail.gmail.com>
Date: Wed, 4 Sep 2024 09:51:56 +0200
From: Geert Uytterhoeven <geert@...ux-m68k.org>
To: Niklas Söderlund <niklas.soderlund+renesas@...natech.se>
Cc: Andrew Lunn <andrew@...n.ch>, 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>, 
	netdev@...r.kernel.org, linux-renesas-soc@...r.kernel.org
Subject: Re: [net-next] net: phy: Check for read errors in SIOCGMIIREG

On Tue, Sep 3, 2024 at 7:16 PM Niklas Söderlund
<niklas.soderlund+renesas@...natech.se> wrote:
> When reading registers from the PHY using the SIOCGMIIREG IOCTL any
> errors returned from either mdiobus_read() or mdiobus_c45_read() are
> ignored, and parts of the returned error is passed as the register value
> back to user-space.
>
> For example, if mdiobus_c45_read() is used with a bus that do not
> implement the read_c45() callback -EOPNOTSUPP is returned. This is
> however directly stored in mii_data->val_out and returned as the
> registers content. As val_out is a u16 the error code is truncated and
> returned as a plausible register value.
>
> Fix this by first checking the return value for errors before returning
> it as the register content.
>
> Before this patch,
>
>     # phytool read eth0/0:1/0
>     0xffa1
>
> After this change,
>
>     $ phytool read eth0/0:1/0
>     error: phy_read (-95)
>
> Signed-off-by: Niklas Söderlund <niklas.soderlund+renesas@...natech.se>

Reviewed-by: Geert Uytterhoeven <geert+renesas@...der.be>

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds