[PATCH net-next] net: sysfs: Implement is_visible for phys_(port_id, port_name, switch_id)

[PATCH net-next] net: sysfs: Implement is_visible for phys_(port_id, port_name, switch_id)

[Yajun Deng]

phys_port_id_show, phys_port_name_show and phys_switch_id_show would
return -EOPNOTSUPP if the netdev didn't implement the corresponding
method.

There is no point in creating these files if they are unsupported.

Put these attributes in netdev_phys_group and implement the is_visible
method. make phys_(port_id, port_name, switch_id) invisible if the netdev
dosen't implement the corresponding method.

Signed-off-by: Yajun Deng <yajun.deng@linux.dev>
---
 include/linux/netdevice.h |  2 +-
 net/core/net-sysfs.c      | 78 +++++++++++++++++++++++++--------------
 2 files changed, 52 insertions(+), 28 deletions(-)

diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index 32a1e41636a9..efbcc4836498 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -2384,7 +2384,7 @@ struct net_device {
 	struct dm_hw_stat_delta __rcu *dm_private;
 #endif
 	struct device		dev;
-	const struct attribute_group *sysfs_groups[4];
+	const struct attribute_group *sysfs_groups[5];
 	const struct attribute_group *sysfs_rx_queue_group;
 
 	const struct rtnl_link_ops *rtnl_link_ops;
diff --git a/net/core/net-sysfs.c b/net/core/net-sysfs.c
index 1ace0cd01adc..f176b7808abe 100644
--- a/net/core/net-sysfs.c
+++ b/net/core/net-sysfs.c
@@ -641,12 +641,6 @@ static ssize_t phys_port_id_show(struct device *dev,
 	struct netdev_phys_item_id ppid;
 	ssize_t ret;
 
-	/* The check is also done in dev_get_phys_port_id; this helps returning
-	 * early without hitting the locking section below.
-	 */
-	if (!netdev->netdev_ops->ndo_get_phys_port_id)
-		return -EOPNOTSUPP;
-
 	ret = sysfs_rtnl_lock(&dev->kobj, &attr->attr, netdev);
 	if (ret)
 		return ret;
@@ -659,7 +653,8 @@ static ssize_t phys_port_id_show(struct device *dev,
 
 	return ret;
 }
-static DEVICE_ATTR_RO(phys_port_id);
+static struct device_attribute dev_attr_phys_port_id =
+	__ATTR(phys_port_id, 0444, phys_port_id_show, NULL);
 
 static ssize_t phys_port_name_show(struct device *dev,
 				   struct device_attribute *attr, char *buf)
@@ -668,13 +663,6 @@ static ssize_t phys_port_name_show(struct device *dev,
 	char name[IFNAMSIZ];
 	ssize_t ret;
 
-	/* The checks are also done in dev_get_phys_port_name; this helps
-	 * returning early without hitting the locking section below.
-	 */
-	if (!netdev->netdev_ops->ndo_get_phys_port_name &&
-	    !netdev->devlink_port)
-		return -EOPNOTSUPP;
-
 	ret = sysfs_rtnl_lock(&dev->kobj, &attr->attr, netdev);
 	if (ret)
 		return ret;
@@ -687,7 +675,8 @@ static ssize_t phys_port_name_show(struct device *dev,
 
 	return ret;
 }
-static DEVICE_ATTR_RO(phys_port_name);
+static struct device_attribute dev_attr_phys_port_name =
+	__ATTR(phys_port_name, 0444, phys_port_name_show, NULL);
 
 static ssize_t phys_switch_id_show(struct device *dev,
 				   struct device_attribute *attr, char *buf)
@@ -696,14 +685,6 @@ static ssize_t phys_switch_id_show(struct device *dev,
 	struct netdev_phys_item_id ppid = { };
 	ssize_t ret;
 
-	/* The checks are also done in dev_get_phys_port_name; this helps
-	 * returning early without hitting the locking section below. This works
-	 * because recurse is false when calling dev_get_port_parent_id.
-	 */
-	if (!netdev->netdev_ops->ndo_get_port_parent_id &&
-	    !netdev->devlink_port)
-		return -EOPNOTSUPP;
-
 	ret = sysfs_rtnl_lock(&dev->kobj, &attr->attr, netdev);
 	if (ret)
 		return ret;
@@ -716,7 +697,52 @@ static ssize_t phys_switch_id_show(struct device *dev,
 
 	return ret;
 }
-static DEVICE_ATTR_RO(phys_switch_id);
+static struct device_attribute dev_attr_phys_switch_id =
+	__ATTR(phys_switch_id, 0444, phys_switch_id_show, NULL);
+
+static struct attribute *netdev_phys_attrs[] __ro_after_init = {
+	&dev_attr_phys_port_id.attr,
+	&dev_attr_phys_port_name.attr,
+	&dev_attr_phys_switch_id.attr,
+	NULL,
+};
+
+static umode_t netdev_phys_is_visible(struct kobject *kobj,
+				      struct attribute *attr, int index)
+{
+	struct device *dev = kobj_to_dev(kobj);
+	struct net_device *netdev = to_net_dev(dev);
+
+	if (attr == &dev_attr_phys_port_id.attr) {
+		/* The check is also done in dev_get_phys_port_id; this helps returning
+		 * early without hitting the locking section below.
+		 */
+		if (!netdev->netdev_ops->ndo_get_phys_port_id)
+			return 0;
+	} else if (attr == &dev_attr_phys_port_name.attr) {
+		/* The checks are also done in dev_get_phys_port_name; this helps
+		 * returning early without hitting the locking section below.
+		 */
+		if (!netdev->netdev_ops->ndo_get_phys_port_name &&
+		    !netdev->devlink_port)
+			return 0;
+	} else if (attr == &dev_attr_phys_switch_id.attr) {
+		/* The checks are also done in dev_get_phys_port_name; this helps
+		 * returning early without hitting the locking section below. This works
+		 * because recurse is false when calling dev_get_port_parent_id.
+		 */
+		if (!netdev->netdev_ops->ndo_get_port_parent_id &&
+		    !netdev->devlink_port)
+			return 0;
+	}
+
+	return attr->mode;
+}
+
+static struct attribute_group netdev_phys_group = {
+	.attrs = netdev_phys_attrs,
+	.is_visible = netdev_phys_is_visible,
+};
 
 static ssize_t threaded_show(struct device *dev,
 			     struct device_attribute *attr, char *buf)
@@ -783,9 +809,6 @@ static struct attribute *net_class_attrs[] __ro_after_init = {
 	&dev_attr_tx_queue_len.attr,
 	&dev_attr_gro_flush_timeout.attr,
 	&dev_attr_napi_defer_hard_irqs.attr,
-	&dev_attr_phys_port_id.attr,
-	&dev_attr_phys_port_name.attr,
-	&dev_attr_phys_switch_id.attr,
 	&dev_attr_proto_down.attr,
 	&dev_attr_carrier_up_count.attr,
 	&dev_attr_carrier_down_count.attr,
@@ -2328,6 +2351,7 @@ int netdev_register_kobject(struct net_device *ndev)
 		groups++;
 
 	*groups++ = &netstat_group;
+	*groups++ = &netdev_phys_group;
 
 	if (wireless_group_needed(ndev))
 		*groups++ = &wireless_group;
-- 
2.25.1

Re: [PATCH net-next] net: sysfs: Implement is_visible for phys_(port_id, port_name, switch_id)

[Jakub Kicinski]

On Thu, 15 May 2025 21:02:05 +0800 Yajun Deng wrote:
> +static struct attribute *netdev_phys_attrs[] __ro_after_init = {

Why __ro_after_init and not const? I can't find the reason with 
a quick grep. This is just an array of pointers, not objects.

> +	&dev_attr_phys_port_id.attr,
> +	&dev_attr_phys_port_name.attr,
> +	&dev_attr_phys_switch_id.attr,
> +	NULL,
> +};
> +
> +static umode_t netdev_phys_is_visible(struct kobject *kobj,
> +				      struct attribute *attr, int index)
> +{
> +	struct device *dev = kobj_to_dev(kobj);
> +	struct net_device *netdev = to_net_dev(dev);
> +
> +	if (attr == &dev_attr_phys_port_id.attr) {
> +		/* The check is also done in dev_get_phys_port_id; this helps returning
> +		 * early without hitting the locking section below.
> +		 */
> +		if (!netdev->netdev_ops->ndo_get_phys_port_id)
> +			return 0;
> +	} else if (attr == &dev_attr_phys_port_name.attr) {
> +		/* The checks are also done in dev_get_phys_port_name; this helps
> +		 * returning early without hitting the locking section below.
> +		 */
> +		if (!netdev->netdev_ops->ndo_get_phys_port_name &&
> +		    !netdev->devlink_port)
> +			return 0;
> +	} else if (attr == &dev_attr_phys_switch_id.attr) {
> +		/* The checks are also done in dev_get_phys_port_name; this helps
> +		 * returning early without hitting the locking section below. This works
> +		 * because recurse is false when calling dev_get_port_parent_id.
> +		 */
> +		if (!netdev->netdev_ops->ndo_get_port_parent_id &&
> +		    !netdev->devlink_port)
> +			return 0;

I'm slightly worried some user space depends on the files existing,
but maybe ENOENT vs EOPNOTSUPP doesn't make a big difference.

Can you remove the comments, tho? I don't think they add much value.
-- 
pw-bot: cr

Re: [PATCH net-next] net: sysfs: Implement is_visible for phys_(port_id, port_name, switch_id)

[Yajun Deng]

May 17, 2025 at 6:26 AM, "Jakub Kicinski" <kuba@kernel.org> wrote:



> 
> On Thu, 15 May 2025 21:02:05 +0800 Yajun Deng wrote:
> 
> > 
> > +static struct attribute *netdev_phys_attrs[] __ro_after_init = {
> > 
> 
> Why __ro_after_init and not const? I can't find the reason with 
> 
> a quick grep. This is just an array of pointers, not objects.
> 

These attributes in net_class_attrs had __ro_after_init before this patch.


> > 
> > + &dev_attr_phys_port_id.attr,
> > 
> >  + &dev_attr_phys_port_name.attr,
> > 
> >  + &dev_attr_phys_switch_id.attr,
> > 
> >  + NULL,
> > 
> >  +};
> > 
> >  +
> > 
> >  +static umode_t netdev_phys_is_visible(struct kobject *kobj,
> > 
> >  + struct attribute *attr, int index)
> > 
> >  +{
> > 
> >  + struct device *dev = kobj_to_dev(kobj);
> > 
> >  + struct net_device *netdev = to_net_dev(dev);
> > 
> >  +
> > 
> >  + if (attr == &dev_attr_phys_port_id.attr) {
> > 
> >  + /* The check is also done in dev_get_phys_port_id; this helps returning
> > 
> >  + * early without hitting the locking section below.
> > 
> >  + */
> > 
> >  + if (!netdev->netdev_ops->ndo_get_phys_port_id)
> > 
> >  + return 0;
> > 
> >  + } else if (attr == &dev_attr_phys_port_name.attr) {
> > 
> >  + /* The checks are also done in dev_get_phys_port_name; this helps
> > 
> >  + * returning early without hitting the locking section below.
> > 
> >  + */
> > 
> >  + if (!netdev->netdev_ops->ndo_get_phys_port_name &&
> > 
> >  + !netdev->devlink_port)
> > 
> >  + return 0;
> > 
> >  + } else if (attr == &dev_attr_phys_switch_id.attr) {
> > 
> >  + /* The checks are also done in dev_get_phys_port_name; this helps
> > 
> >  + * returning early without hitting the locking section below. This works
> > 
> >  + * because recurse is false when calling dev_get_port_parent_id.
> > 
> >  + */
> > 
> >  + if (!netdev->netdev_ops->ndo_get_port_parent_id &&
> > 
> >  + !netdev->devlink_port)
> > 
> >  + return 0;
> > 
> 
> I'm slightly worried some user space depends on the files existing,
> 
> but maybe ENOENT vs EOPNOTSUPP doesn't make a big difference.
> 
> Can you remove the comments, tho? I don't think they add much value.
> 
Okay.

> -- 
> 
> pw-bot: cr
>