netdev - Re: [PATCH v9 net-next 12/12] net: remove phy_has_hwtstamp() -> phy_mii

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Date: Thu, 28 Sep 2023 12:12:14 +0200
From: Köry Maincent <kory.maincent@...tlin.com>
To: Vladimir Oltean <vladimir.oltean@....com>
Cc: netdev@...r.kernel.org, "David S. Miller" <davem@...emloft.net>, Eric
 Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>, Paolo
 Abeni <pabeni@...hat.com>, Andrew Lunn <andrew@...n.ch>, Florian Fainelli
 <f.fainelli@...il.com>, Maxim Georgiev <glipus@...il.com>, Horatiu Vultur
 <horatiu.vultur@...rochip.com>, Maxime Chevallier
 <maxime.chevallier@...tlin.com>, Richard Cochran
 <richardcochran@...il.com>, Vadim Fedorenko <vadim.fedorenko@...ux.dev>,
 Gerhard Engleder <gerhard@...leder-embedded.com>, Hangbin Liu
 <liuhangbin@...il.com>, Russell King <linux@...linux.org.uk>, Heiner
 Kallweit <hkallweit1@...il.com>, Jacob Keller <jacob.e.keller@...el.com>,
 Jay Vosburgh <j.vosburgh@...il.com>, Andy Gospodarek <andy@...yhouse.net>,
 Wei Fang <wei.fang@....com>, Shenwei Wang <shenwei.wang@....com>, Clark
 Wang <xiaoning.wang@....com>, NXP Linux Team <linux-imx@....com>,
 UNGLinuxDriver@...rochip.com, Lars Povlsen <lars.povlsen@...rochip.com>,
 Steen Hegelund <Steen.Hegelund@...rochip.com>, Daniel Machon
 <daniel.machon@...rochip.com>, Simon Horman <simon.horman@...igine.com>,
 Casper Andersson <casper.casan@...il.com>, Sergey Organov
 <sorganov@...il.com>, Michal Kubecek <mkubecek@...e.cz>,
 linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v9 net-next 12/12] net: remove phy_has_hwtstamp() ->
 phy_mii_ioctl() decision from converted drivers

On Tue,  1 Aug 2023 17:28:24 +0300
Vladimir Oltean <vladimir.oltean@....com> wrote:

> It is desirable that the new .ndo_hwtstamp_set() API gives more
> uniformity, less overhead and future flexibility w.r.t. the PHY
> timestamping behavior.
> 
> Currently there are some drivers which allow PHY timestamping through
> the procedure mentioned in Documentation/networking/timestamping.rst.
> They don't do anything locally if phy_has_hwtstamp() is set, except for
> lan966x which installs PTP packet traps.
> 
> Centralize that behavior in a new dev_set_hwtstamp_phylib() code
> function, which calls either phy_mii_ioctl() for the phylib PHY,
> or .ndo_hwtstamp_set() of the netdev, based on a single policy
> (currently simplistic: phy_has_hwtstamp()).
> 
> Any driver converted to .ndo_hwtstamp_set() will automatically opt into
> the centralized phylib timestamping policy. Unconverted drivers still
> get to choose whether they let the PHY handle timestamping or not.
> 
> Netdev drivers with integrated PHY drivers that don't use phylib
> presumably don't set dev->phydev, and those will always see
> HWTSTAMP_SOURCE_NETDEV requests even when converted. The timestamping
> policy will remain 100% up to them.

> +static int dev_set_hwtstamp_phylib(struct net_device *dev,
> +				   struct kernel_hwtstamp_config *cfg,
> +				   struct netlink_ext_ack *extack)
> +{
...

> +	if (phy_ts) {
> +		err = phy_hwtstamp_set(dev->phydev, cfg, extack);
> +		if (err) {
> +			if (changed)
> +				ops->ndo_hwtstamp_set(dev, &old_cfg, NULL);
> +			return err;
> +		}
> +	}

In this case the copy_from_user function will be call 2 times, one in
dev_set_hwtstamp and one in the mii_ts.hwtstamp callback of the PHY driver.
Should we create also a copied_from_user flag? Other idea?

Regards,