Re: [PATCH net-next 1/2] net: provide a default dev->ethtool_ops

From: Eric Dumazet <edumazet@google.com>

Instead of forcing device drivers to provide empty ethtool_ops or tweak
net/core/ethtool.c again, we could provide a generic ethtool_ops.

This occurred to me when I wanted to add GSO support to GRE tunnels.
ethtool -k support should be generic for all drivers.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Maciej Żenczykowski <redacted>
---
 net/core/dev.c     |    5 +++
 net/core/ethtool.c |   54 +++++++++++++++++--------------------------
 2 files changed, 27 insertions(+), 32 deletions(-)

diff --git a/net/core/dev.c b/net/core/dev.c
index b1e6d63..ff8dcfc 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c

@@ -6045,6 +6045,11 @@ struct net_device *alloc_netdev_mqs(int sizeof_priv, const char *name,

        strcpy(dev->name, name);
        dev->group = INIT_NETDEV_GROUP;
+       if (!dev->ethtool_ops) {
+               static const struct ethtool_ops default_ethtool_ops;
+
+               dev->ethtool_ops = &default_ethtool_ops;
+       }
        return dev;

 free_all:

diff --git a/net/core/ethtool.c b/net/core/ethtool.c
index cbf033d..aef0162 100644
--- a/net/core/ethtool.c
+++ b/net/core/ethtool.c

@@ -175,7 +175,7 @@ static int __ethtool_get_sset_count(struct net_device *dev, int sset)
        if (sset == ETH_SS_FEATURES)
                return ARRAY_SIZE(netdev_features_strings);

-       if (ops && ops->get_sset_count && ops->get_strings)
+       if (ops->get_sset_count && ops->get_strings)
                return ops->get_sset_count(dev, sset);
        else
                return -EOPNOTSUPP;

@@ -311,7 +311,7 @@ int __ethtool_get_settings(struct net_device *dev, struct ethtool_cmd *cmd)
 {
        ASSERT_RTNL();

-       if (!dev->ethtool_ops || !dev->ethtool_ops->get_settings)
+       if (!dev->ethtool_ops->get_settings)
                return -EOPNOTSUPP;

        memset(cmd, 0, sizeof(struct ethtool_cmd));

@@ -355,7 +355,7 @@ static noinline_for_stack int ethtool_get_drvinfo(struct net_device *dev,

        memset(&info, 0, sizeof(info));
        info.cmd = ETHTOOL_GDRVINFO;
-       if (ops && ops->get_drvinfo) {
+       if (ops->get_drvinfo) {
                ops->get_drvinfo(dev, &info);
        } else if (dev->dev.parent && dev->dev.parent->driver) {
                strlcpy(info.bus_info, dev_name(dev->dev.parent),

@@ -370,7 +370,7 @@ static noinline_for_stack int ethtool_get_drvinfo(struct net_device *dev,
         * this method of obtaining string set info is deprecated;
         * Use ETHTOOL_GSSET_INFO instead.
         */
-       if (ops && ops->get_sset_count) {
+       if (ops->get_sset_count) {
                int rc;

                rc = ops->get_sset_count(dev, ETH_SS_TEST);

@@ -383,9 +383,9 @@ static noinline_for_stack int ethtool_get_drvinfo(struct net_device *dev,
                if (rc >= 0)
                        info.n_priv_flags = rc;
        }
-       if (ops && ops->get_regs_len)
+       if (ops->get_regs_len)
                info.regdump_len = ops->get_regs_len(dev);
-       if (ops && ops->get_eeprom_len)
+       if (ops->get_eeprom_len)
                info.eedump_len = ops->get_eeprom_len(dev);

        if (copy_to_user(useraddr, &info, sizeof(info)))

@@ -1275,7 +1275,7 @@ static int ethtool_get_dump_flag(struct net_device *dev,
        struct ethtool_dump dump;
        const struct ethtool_ops *ops = dev->ethtool_ops;

-       if (!dev->ethtool_ops->get_dump_flag)
+       if (!ops->get_dump_flag)
                return -EOPNOTSUPP;

        if (copy_from_user(&dump, useraddr, sizeof(dump)))

@@ -1299,8 +1299,7 @@ static int ethtool_get_dump_data(struct net_device *dev,
        const struct ethtool_ops *ops = dev->ethtool_ops;
        void *data = NULL;

-       if (!dev->ethtool_ops->get_dump_data ||
-               !dev->ethtool_ops->get_dump_flag)
+       if (!ops->get_dump_data || !ops->get_dump_flag)
                return -EOPNOTSUPP;

        if (copy_from_user(&dump, useraddr, sizeof(dump)))

@@ -1349,7 +1348,7 @@ static int ethtool_get_ts_info(struct net_device *dev, void __user *useraddr)

                err = phydev->drv->ts_info(phydev, &info);

-       } else if (dev->ethtool_ops && dev->ethtool_ops->get_ts_info) {
+       } else if (ops->get_ts_info) {

                err = ops->get_ts_info(dev, &info);

@@ -1410,8 +1409,9 @@ static int ethtool_get_module_eeprom(struct net_device *dev,
                                      modinfo.eeprom_len);
 }

-/* The main entry point in this file.  Called from net/core/dev.c */
-
+/* The main entry point in this file.  Called from net/core/dev.c
+ * with RTNL held.
+ */
 int dev_ethtool(struct net *net, struct ifreq *ifr)
 {
        struct net_device *dev = __dev_get_by_name(net, ifr->ifr_name);

@@ -1419,25 +1419,15 @@ int dev_ethtool(struct net *net, struct ifreq *ifr)
        u32 ethcmd;
        int rc;
        u32 old_features;
+       const struct ethtool_ops *ops;

        if (!dev || !netif_device_present(dev))
                return -ENODEV;

+       ops = dev->ethtool_ops;
        if (copy_from_user(&ethcmd, useraddr, sizeof(ethcmd)))
                return -EFAULT;

-       if (!dev->ethtool_ops) {
-               /* A few commands do not require any driver support,
-                * are unprivileged, and do not change anything, so we
-                * can take a shortcut to them. */
-               if (ethcmd == ETHTOOL_GDRVINFO)
-                       return ethtool_get_drvinfo(dev, useraddr);
-               else if (ethcmd == ETHTOOL_GET_TS_INFO)
-                       return ethtool_get_ts_info(dev, useraddr);
-               else
-                       return -EOPNOTSUPP;
-       }
-
        /* Allow some commands to be done by anyone */
        switch (ethcmd) {
        case ETHTOOL_GSET:

@@ -1476,8 +1466,8 @@ int dev_ethtool(struct net *net, struct ifreq *ifr)
                        return -EPERM;
        }

-       if (dev->ethtool_ops->begin) {
-               rc = dev->ethtool_ops->begin(dev);
+       if (ops->begin) {
+               rc = ops->begin(dev);
                if (rc  < 0)
                        return rc;
        }

@@ -1504,11 +1494,11 @@ int dev_ethtool(struct net *net, struct ifreq *ifr)
                break;
        case ETHTOOL_GMSGLVL:
                rc = ethtool_get_value(dev, useraddr, ethcmd,
-                                      dev->ethtool_ops->get_msglevel);
+                                      ops->get_msglevel);
                break;
        case ETHTOOL_SMSGLVL:
                rc = ethtool_set_value_void(dev, useraddr,
-                                      dev->ethtool_ops->set_msglevel);
+                                           ops->set_msglevel);
                break;
        case ETHTOOL_GEEE:
                rc = ethtool_get_eee(dev, useraddr);

@@ -1570,11 +1560,11 @@ int dev_ethtool(struct net *net, struct ifreq *ifr)
                break;
        case ETHTOOL_GPFLAGS:
                rc = ethtool_get_value(dev, useraddr, ethcmd,
-                                      dev->ethtool_ops->get_priv_flags);
+                                      ops->get_priv_flags);
                break;
        case ETHTOOL_SPFLAGS:
                rc = ethtool_set_value(dev, useraddr,
-                                      dev->ethtool_ops->set_priv_flags);
+                                      ops->set_priv_flags);
                break;
        case ETHTOOL_GRXFH:
        case ETHTOOL_GRXRINGS:

@@ -1655,8 +1645,8 @@ int dev_ethtool(struct net *net, struct ifreq *ifr)
                rc = -EOPNOTSUPP;
        }

-       if (dev->ethtool_ops->complete)
-               dev->ethtool_ops->complete(dev);
+       if (ops->complete)
+               ops->complete(dev);

        if (old_features != dev->features)
                netdev_features_change(dev);