[PATCH v2 0/2] net: phy: relax error checking when creating sysfs link netdev->phydev

Some ethernet drivers (like TI CPSW) may connect and manage >1 Net PHYs per
one netdevice, as result such drivers will produce warning during system
boot and fail to connect second phy to netdevice when PHYLIB framework
will try to create sysfs link netdev->phydev for second PHY
in phy_attach_direct(), because sysfs link with the same name has been
created already for the first PHY.
As result, second CPSW external port will became unusable.
This regression was introduced by commits:
5568363f0cb3 ("net: phy: Create sysfs reciprocal links for attached_dev/phydev"
a3995460491d ("net: phy: Relax error checking on sysfs_create_link()"

Patch 1: exports sysfs_create_link_nowarn() function as preparation for Patch 2.
Patch 2: relaxes error checking when PHYLIB framework is creating sysfs
link netdev->phydev in phy_attach_direct(), suppresses warning by using
sysfs_create_link_nowarn() and adds error message instead, so links creation
failure is not fatal any more and system can continue working,
which fixes TI CPSW issue and makes boot logs accessible
in case of NFS boot, for example.

This can be stable material 4.13+.

Changes in v2:
- commit messages updated.

v1: 
 https://patchwork.ozlabs.org/cover/886058/

Cc: Florian Fainelli <f.fainelli@gmail.com>
Cc: Andrew Lunn <andrew@lunn.ch>
Grygorii Strashko (2):
  sysfs: symlink: export sysfs_create_link_nowarn()
  net: phy: relax error checking when creating sysfs link netdev->phydev

 drivers/net/phy/phy_device.c | 15 +++++++++++----
 fs/sysfs/symlink.c           |  1 +
 2 files changed, 12 insertions(+), 4 deletions(-)

-- 
2.10.5

The sysfs_create_link_nowarn() is going to be used in phylib framework in
subsequent patch which can be built as module. Hence, export
sysfs_create_link_nowarn() to avoid build errors.

Cc: Florian Fainelli <f.fainelli@gmail.com>
Cc: Andrew Lunn <andrew@lunn.ch>
Fixes: a3995460491d ("net: phy: Relax error checking on sysfs_create_link()")
Signed-off-by: Grygorii Strashko <grygorii.strashko@ti.com>
---
"Fixes" added as there is dependency this and subsequent patch.
 fs/sysfs/symlink.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/fs/sysfs/symlink.c b/fs/sysfs/symlink.c
index 8664db2..215c225 100644
--- a/fs/sysfs/symlink.c
+++ b/fs/sysfs/symlink.c

@@ -106,6 +106,7 @@ int sysfs_create_link_nowarn(struct kobject *kobj, struct kobject *target,
 {
 	return sysfs_do_create_link(kobj, target, name, 0);
 }
+EXPORT_SYMBOL_GPL(sysfs_create_link_nowarn);
 
 /**
  *	sysfs_delete_link - remove symlink in object's directory.

-- 
2.10.5

Some ethernet drivers (like TI CPSW) may connect and manage >1 Net PHYs per
one netdevice, as result such drivers will produce warning during system
boot and fail to connect second phy to netdevice when PHYLIB framework
will try to create sysfs link netdev->phydev for second PHY
in phy_attach_direct(), because sysfs link with the same name has been
created already for the first PHY. As result, second CPSW external
port will became unusable.

Fix it by relaxing error checking when PHYLIB framework is creating sysfs
link netdev->phydev in phy_attach_direct(), suppressing warning by using
sysfs_create_link_nowarn() and adding error message instead.
After this change links (phy->netdev and netdev->phy) creation failure is not
fatal any more and system can continue working, which fixes TI CPSW issue.

Cc: Florian Fainelli <f.fainelli@gmail.com>
Cc: Andrew Lunn <andrew@lunn.ch>
Fixes: a3995460491d ("net: phy: Relax error checking on sysfs_create_link()")
Signed-off-by: Grygorii Strashko <grygorii.strashko@ti.com>
---
 drivers/net/phy/phy_device.c | 15 +++++++++++----
 1 file changed, 11 insertions(+), 4 deletions(-)

diff --git a/drivers/net/phy/phy_device.c b/drivers/net/phy/phy_device.c
index 478405e..fe16f58 100644
--- a/drivers/net/phy/phy_device.c
+++ b/drivers/net/phy/phy_device.c

@@ -1012,10 +1012,17 @@ int phy_attach_direct(struct net_device *dev, struct phy_device *phydev,
 	err = sysfs_create_link(&phydev->mdio.dev.kobj, &dev->dev.kobj,
 				"attached_dev");
 	if (!err) {
-		err = sysfs_create_link(&dev->dev.kobj, &phydev->mdio.dev.kobj,
-					"phydev");
-		if (err)
-			goto error;
+		err = sysfs_create_link_nowarn(&dev->dev.kobj,
+					       &phydev->mdio.dev.kobj,
+					       "phydev");
+		if (err) {
+			dev_err(&dev->dev, "could not add device link to %s err %d\n",
+				kobject_name(&phydev->mdio.dev.kobj),
+				err);
+			/* non-fatal - some net drivers can use one netdevice
+			 * with more then one phy
+			 */
+		}
 
 		phydev->sysfs_links = true;
 	}

-- 
2.10.5

On Fri, Mar 16, 2018 at 05:08:34PM -0500, Grygorii Strashko wrote:

The sysfs_create_link_nowarn() is going to be used in phylib framework in
subsequent patch which can be built as module. Hence, export
sysfs_create_link_nowarn() to avoid build errors.

Cc: Florian Fainelli <f.fainelli@gmail.com>
Cc: Andrew Lunn <andrew@lunn.ch>
Fixes: a3995460491d ("net: phy: Relax error checking on sysfs_create_link()")

This specific patch doesn't fix anything, it just _allows_ it to be
fixed in the second patch :)

Anyway, just a nit...

Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

From: Grygorii Strashko <grygorii.strashko@ti.com>
Date: Fri, 16 Mar 2018 17:08:33 -0500

Some ethernet drivers (like TI CPSW) may connect and manage >1 Net PHYs per
one netdevice, as result such drivers will produce warning during system
boot and fail to connect second phy to netdevice when PHYLIB framework
will try to create sysfs link netdev->phydev for second PHY
in phy_attach_direct(), because sysfs link with the same name has been
created already for the first PHY.
As result, second CPSW external port will became unusable.
This regression was introduced by commits:
5568363f0cb3 ("net: phy: Create sysfs reciprocal links for attached_dev/phydev"
a3995460491d ("net: phy: Relax error checking on sysfs_create_link()"

Patch 1: exports sysfs_create_link_nowarn() function as preparation for Patch 2.
Patch 2: relaxes error checking when PHYLIB framework is creating sysfs
link netdev->phydev in phy_attach_direct(), suppresses warning by using
sysfs_create_link_nowarn() and adds error message instead, so links creation
failure is not fatal any more and system can continue working,
which fixes TI CPSW issue and makes boot logs accessible
in case of NFS boot, for example.

Series applied and queued up for -stable, thanks.