Re: [PATCH v9 net-next 12/12] net: remove phy_has_hwtstamp() -> phy_mii_ioctl() decision from converted drivers

From: "Köry Maincent" <kory.maincent@bootlin.com>
To: Vladimir Oltean <vladimir.oltean@nxp.com>
Cc: netdev@vger.kernel.org, "David S. Miller" <davem@davemloft.net>,
	Eric Dumazet <edumazet@google.com>,
	Jakub Kicinski <kuba@kernel.org>, Paolo Abeni <pabeni@redhat.com>,
	Andrew Lunn <andrew@lunn.ch>,
	Florian Fainelli <f.fainelli@gmail.com>,
	Maxim Georgiev <glipus@gmail.com>,
	Horatiu Vultur <horatiu.vultur@microchip.com>,
	Maxime Chevallier <maxime.chevallier@bootlin.com>,
	Richard Cochran <richardcochran@gmail.com>,
	Vadim Fedorenko <vadim.fedorenko@linux.dev>,
	Gerhard Engleder <gerhard@engleder-embedded.com>,
	Hangbin Liu <liuhangbin@gmail.com>,
	Russell King <linux@armlinux.org.uk>,
	Heiner Kallweit <hkallweit1@gmail.com>,
	Jacob Keller <jacob.e.keller@intel.com>,
	Jay Vosburgh <j.vosburgh@gmail.com>,
	Andy Gospodarek <andy@greyhouse.net>, Wei Fang <wei.fang@nxp.com>,
	Shenwei Wang <shenwei.wang@nxp.com>,
	Clark Wang <xiaoning.wang@nxp.com>,
	NXP Linux Team <linux-imx@nxp.com>,
	UNGLinuxDriver@microchip.com,
	Lars Povlsen <lars.povlsen@microchip.com>,
	Steen Hegelund <Steen.Hegelund@microchip.com>,
	Daniel Machon <daniel.machon@microchip.com>,
	Simon Horman <simon.horman@corigine.com>,
	Casper Andersson <casper.casan@gmail.com>,
	Sergey Organov <sorganov@gmail.com>,
	Michal Kubecek <mkubecek@suse.cz>,
	linux-arm-kernel@lists.infradead.org,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH v9 net-next 12/12] net: remove phy_has_hwtstamp() -> phy_mii_ioctl() decision from converted drivers
Date: Thu, 28 Sep 2023 14:39:58 +0200	[thread overview]
Message-ID: <20230928143958.298ee225@kmaincent-XPS-13-7390> (raw)
In-Reply-To: <20230928121214.170e31b0@kmaincent-XPS-13-7390>

On Thu, 28 Sep 2023 12:12:14 +0200
Köry Maincent <kory.maincent@bootlin.com> wrote:

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

oops sorry for the noise the issue I face seems elsewhere.
If I understand it well, two call of copy_from_user consecutive will behave the
same.

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