linux-kernel - Re: [PATCH 15/16] net: phy: adin: add ethtool get

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Message-ID: <ce952e3f8d927cdbccb268d708b4e47179d69b06.camel@analog.com>
Date:   Tue, 6 Aug 2019 07:11:57 +0000
From:   "Ardelean, Alexandru" <alexandru.Ardelean@...log.com>
To:     "andrew@...n.ch" <andrew@...n.ch>
CC:     "davem@...emloft.net" <davem@...emloft.net>,
        "hkallweit1@...il.com" <hkallweit1@...il.com>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "mark.rutland@....com" <mark.rutland@....com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "f.fainelli@...il.com" <f.fainelli@...il.com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "robh+dt@...nel.org" <robh+dt@...nel.org>
Subject: Re: [PATCH 15/16] net: phy: adin: add ethtool get_stats support

On Mon, 2019-08-05 at 17:28 +0200, Andrew Lunn wrote:
> [External]
> 
> > +struct adin_hw_stat {
> > +	const char *string;
> > +static void adin_get_strings(struct phy_device *phydev, u8 *data)
> > +{
> > +	int i;
> > +
> > +	for (i = 0; i < ARRAY_SIZE(adin_hw_stats); i++) {
> > +		memcpy(data + i * ETH_GSTRING_LEN,
> > +		       adin_hw_stats[i].string, ETH_GSTRING_LEN);
> 
> You define string as a char *. So it will be only as long as it should
> be. However memcpy always copies ETH_GSTRING_LEN bytes, doing off the
> end of the string and into whatever follows.
> 

hmm, will use strlcpy()
i blindedly copied memcpy() from some other driver

> 
> > +	}
> > +}
> > +
> > +static int adin_read_mmd_stat_regs(struct phy_device *phydev,
> > +				   struct adin_hw_stat *stat,
> > +				   u32 *val)
> > +{
> > +	int ret;
> > +
> > +	ret = phy_read_mmd(phydev, MDIO_MMD_VEND1, stat->reg1);
> > +	if (ret < 0)
> > +		return ret;
> > +
> > +	*val = (ret & 0xffff);
> > +
> > +	if (stat->reg2 == 0)
> > +		return 0;
> > +
> > +	ret = phy_read_mmd(phydev, MDIO_MMD_VEND1, stat->reg2);
> > +	if (ret < 0)
> > +		return ret;
> > +
> > +	*val <<= 16;
> > +	*val |= (ret & 0xffff);
> 
> Does the hardware have a snapshot feature? Is there a danger that
> between the two reads stat->reg1 rolls over and you end up with too
> big a value?

i'm afraid i don't understand about the snapshot feature you are mentioning;
i.e. i don't remember seeing it in other chips;

regarding the danger that stat->reg1 rolls over, i guess that is possible, but it's a bit hard to guard against;
i guess if it ends up in that scenario, [for many counters] things would be horribly bad, and the chip, or cabling would
be unusable;

not sure if this answer is sufficient/satisfactory;

thanks

> 
>     Andrew