linux-kernel - Re: [PATCH net v2 2/2] net: usb: asix: ax88772: Increase phy

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Message-ID: <Z9rYHDL3dNbaK9jZ@shell.armlinux.org.uk>
Date: Wed, 19 Mar 2025 14:43:40 +0000
From: "Russell King (Oracle)" <linux@...linux.org.uk>
To: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Cc: linux-usb@...r.kernel.org, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org, Andrew Lunn <andrew+netdev@...n.ch>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	Heiner Kallweit <hkallweit1@...il.com>
Subject: Re: [PATCH net v2 2/2] net: usb: asix: ax88772: Increase phy_name
 size

On Wed, Mar 19, 2025 at 12:54:34PM +0200, Andy Shevchenko wrote:
> GCC compiler (Debian 14.2.0-17) is not happy about printing
> into a short buffer (when build with `make W=1`):
> 
>  drivers/net/usb/ax88172a.c: In function ‘ax88172a_reset’:
>  include/linux/phy.h:312:20: error: ‘%s’ directive output may be truncated writing up to 60 bytes into a region of size 20 [-Werror=format-truncation=]

GCC reckons this can be up to 60 bytes...

>  struct ax88172a_private {
>  	struct mii_bus *mdio;
>  	struct phy_device *phydev;
> -	char phy_name[20];
> +	char phy_name[MII_BUS_ID_SIZE + 3];

MII_BUS_ID_SIZE is sized to 61, and is what is used in struct
mii_bus::id. Why there a +3 here, which seems like a random constant to
make it 64-bit aligned in size. If we have need to increase
MII_BUS_ID_SIZE in the future, this kind of alignment then goes
wrong...

If the intention is to align it to 64-bit then there's surely a better
and future-proof ways to do that.

I'm also surprised that the +3 randomness wasn't described in the
commit message.

> @@ -210,7 +210,10 @@ static int ax88172a_bind(struct usbnet *dev, struct usb_interface *intf)
>  	ret = asix_read_phy_addr(dev, priv->use_embdphy);
>  	if (ret < 0)
>  		goto free;
> -
> +	if (ret >= PHY_MAX_ADDR) {
> +		netdev_err(dev->net, "Invalid PHY ID %x\n", ret);

An address is not a "PHY ID". "Invalid PHY address %d\n" probably makes
more sense, but if you want to keep the hex, then it really should be
%#x or 0x%x to make it clear that e.g. "20" is hex and not decimal.

-- 
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
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