On Fri, 22 Feb 2019 11:04:50 +0100, Michal Kubecek wrote:

On Thu, Feb 21, 2019 at 09:46:19AM -0800, Jakub Kicinski wrote:

quoted

Support getting devlink instance from a new NDO.

Signed-off-by: Jakub Kicinski <redacted>
---
 drivers/net/ethernet/netronome/nfp/nfp_app.h        |  2 ++
 drivers/net/ethernet/netronome/nfp/nfp_devlink.c    | 11 +++++++++++
 drivers/net/ethernet/netronome/nfp/nfp_net_common.c |  1 +
 drivers/net/ethernet/netronome/nfp/nfp_net_repr.c   |  1 +
 4 files changed, 15 insertions(+)

diff --git a/drivers/net/ethernet/netronome/nfp/nfp_app.h b/drivers/net/ethernet/netronome/nfp/nfp_app.h
index d578d856a009..f8d422713705 100644
--- a/drivers/net/ethernet/netronome/nfp/nfp_app.h
+++ b/drivers/net/ethernet/netronome/nfp/nfp_app.h

@@ -433,4 +433,6 @@ int nfp_app_nic_vnic_alloc(struct nfp_app *app, struct nfp_net *nn,
 int nfp_app_nic_vnic_init_phy_port(struct nfp_pf *pf, struct nfp_app *app,
 				   struct nfp_net *nn, unsigned int id);
 
+struct devlink *nfp_devlink_get_devlink(struct net_device *netdev);
+
 #endif

diff --git a/drivers/net/ethernet/netronome/nfp/nfp_devlink.c b/drivers/net/ethernet/netronome/nfp/nfp_devlink.c
index db2da99f6aa7..e9eca99cf493 100644
--- a/drivers/net/ethernet/netronome/nfp/nfp_devlink.c
+++ b/drivers/net/ethernet/netronome/nfp/nfp_devlink.c

@@ -376,3 +376,14 @@ void nfp_devlink_port_unregister(struct nfp_port *port)
 {
 	devlink_port_unregister(&port->dl_port);
 }
+
+struct devlink *nfp_devlink_get_devlink(struct net_device *netdev)
+{
+	struct nfp_app *app;
+
+	app = nfp_app_from_netdev(netdev);
+	if (!app)
+		return NULL;
+
+	return priv_to_devlink(app->pf);
+}  

AFAICS this would return a pointer to zero initialized struct devlink
when built with CONFIG_DEVLINK=n. Then devlink_compat_running_version()
would execute

	if (!dev->netdev_ops->ndo_get_devlink)
		return;

	devlink = dev->netdev_ops->ndo_get_devlink(dev);
	if (!devlink || !devlink->ops->info_get)
		return;

with non-null devlink but null devlink->ops so that it dereferences null
pointer (and so does devlink_compat_flash_update()).

devlink_compat_flash_update() is this if CONFIG_DEVLINK=n:

static inline int
devlink_compat_flash_update(struct net_device *dev, const char *file_name)
{
	return -EOPNOTSUPP;
}

No?

Maybe it would be safer not to call ndo_get_devlink directly and have
an inline wrapper like

#if IS_ENABLED(CONFIG_NET_DEVLINK)
static inline struct devlink *dev_get_devlink(struct net_device *dev)
{
	if (dev->netdev_ops->ndo_get_devlink)
		return dev->netdev_ops->ndo_get_devlink();
	else
		retrurn NULL;
}
#else
static inline struct devlink *dev_get_devlink(struct net_device *dev)
{
	return NULL;
}
#endif

so that one can simply call the wrapper and check return value for NULL.

Only devlink code can call this ndo, and it doesn't exist with
DEVLINK=n.  I don't dislike wrappers for NDOs, but I'll defer to Jiri
to decide if we want a wrapper here (without the #if/#else, just the
first part for code clarity) :)