netdev - RE: [PATCH v2 2/4] net: Expose available time stamping layers to user space.

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Date:   Fri, 03 Mar 2023 18:56:53 -0500
From:   Willem de Bruijn <willemdebruijn.kernel@...il.com>
To:     Köry Maincent <kory.maincent@...tlin.com>,
        linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
        linux-omap@...r.kernel.org
Cc:     Michael Walle <michael@...le.cc>,
        Richard Cochran <richardcochran@...il.com>,
        Kory Maincent <kory.maincent@...tlin.com>,
        thomas.petazzoni@...tlin.com, Jay Vosburgh <j.vosburgh@...il.com>,
        Veaceslav Falico <vfalico@...il.com>,
        Andy Gospodarek <andy@...yhouse.net>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Joakim Zhang <qiangqing.zhang@....com>,
        Vladimir Oltean <vladimir.oltean@....com>,
        Claudiu Manoil <claudiu.manoil@....com>,
        Alexandre Belloni <alexandre.belloni@...tlin.com>,
        UNGLinuxDriver@...rochip.com,
        Grygorii Strashko <grygorii.strashko@...com>,
        Andrew Lunn <andrew@...n.ch>,
        Heiner Kallweit <hkallweit1@...il.com>,
        Russell King <linux@...linux.org.uk>,
        Minghao Chi <chi.minghao@....com.cn>,
        Guangbin Huang <huangguangbin2@...wei.com>,
        Jie Wang <wangjie125@...wei.com>,
        Wolfram Sang <wsa+renesas@...g-engineering.com>,
        Sven Eckelmann <sven@...fation.org>,
        Wang Yufen <wangyufen@...wei.com>,
        Oleksij Rempel <linux@...pel-privat.de>,
        Alexandru Tachici <alexandru.tachici@...log.com>
Subject: RE: [PATCH v2 2/4] net: Expose available time stamping layers to user
 space.

Köry Maincent wrote:
> From: Richard Cochran <richardcochran@...il.com>
> 
> Time stamping on network packets may happen either in the MAC or in
> the PHY, but not both.  In preparation for making the choice
> selectable, expose both the current and available layers via sysfs.
> 
> In accordance with the kernel implementation as it stands, the current
> layer will always read as "phy" when a PHY time stamping device is
> present.  Future patches will allow changing the current layer
> administratively.
> 
> Signed-off-by: Richard Cochran <richardcochran@...il.com>
> Signed-off-by: Kory Maincent <kory.maincent@...tlin.com>
> ---
> 
> Notes:
>     Changes in v2:
>     - Move the introduction of selected_timestamping_layer variable in next
>       patch.
> 
>  .../ABI/testing/sysfs-class-net-timestamping  | 17 ++++++
>  net/core/net-sysfs.c                          | 60 +++++++++++++++++++
>  2 files changed, 77 insertions(+)
>  create mode 100644 Documentation/ABI/testing/sysfs-class-net-timestamping
> 
> diff --git a/Documentation/ABI/testing/sysfs-class-net-timestamping b/Documentation/ABI/testing/sysfs-class-net-timestamping
> new file mode 100644
> index 000000000000..529c3a6eb607
> --- /dev/null
> +++ b/Documentation/ABI/testing/sysfs-class-net-timestamping
> @@ -0,0 +1,17 @@
> +What:		/sys/class/net/<iface>/available_timestamping_providers
> +Date:		January 2022
> +Contact:	Richard Cochran <richardcochran@...il.com>
> +Description:
> +		Enumerates the available providers for SO_TIMESTAMPING.
> +		The possible values are:
> +		- "mac"  The MAC provides time stamping.
> +		- "phy"  The PHY or MII device provides time stamping.
> +
> +What:		/sys/class/net/<iface>/current_timestamping_provider
> +Date:		January 2022
> +Contact:	Richard Cochran <richardcochran@...il.com>
> +Description:
> +		Show the current SO_TIMESTAMPING provider.
> +		The possible values are:
> +		- "mac"  The MAC provides time stamping.
> +		- "phy"  The PHY or MII device provides time stamping.
> diff --git a/net/core/net-sysfs.c b/net/core/net-sysfs.c
> index 8409d41405df..26095634fb31 100644
> --- a/net/core/net-sysfs.c
> +++ b/net/core/net-sysfs.c
> @@ -620,6 +620,64 @@ static ssize_t threaded_store(struct device *dev,
>  }
>  static DEVICE_ATTR_RW(threaded);
>  
> +static ssize_t available_timestamping_providers_show(struct device *dev,
> +						     struct device_attribute *attr,
> +						     char *buf)
> +{
> +	const struct ethtool_ops *ops;
> +	struct net_device *netdev;
> +	struct phy_device *phydev;
> +	int ret = 0;
> +
> +	netdev = to_net_dev(dev);
> +	phydev = netdev->phydev;
> +	ops = netdev->ethtool_ops;
> +
> +	if (!rtnl_trylock())
> +		return restart_syscall();
> +
> +	ret += sprintf(buf, "%s\n", "mac");
> +	buf += 4;
> +

Should advertising mac be subject to having ops->get_ts_info?

> +	if (phy_has_tsinfo(phydev)) {
> +		ret += sprintf(buf, "%s\n", "phy");
> +		buf += 4;
> +	}
> +
> +	rtnl_unlock();
> +
> +	return ret;
> +}
> +static DEVICE_ATTR_RO(available_timestamping_providers);