Re: [PATCH net-next v2 1/3] net: netdevsim: Add PHY support in netdevsim

On Tue, 8 Jul 2025 13:55:28 +0200 Maxime Chevallier maxime.chevallier@bootlin.com wrote:

With the introduction of phy_link_topology, we have the ability to keep track of PHY devices that sit behind a net_device. While we still can only attach one single PHY to a netdev, we can look at all these PHYs through netlink, with the ETHTOOL_MSG_PHY_GET command.

Moreover, netlink commands that are targeting PHY devices also now allow specifying which PHY we want to address in a given netlink command.

That whole process comes with its own complexity, and a few bugs were dicovered over the months following the introduction of phy_link_topology.

As devices with multiple PHYs are fairly uncommon, testing the corner cases of multi-phy setups proves to be difficult.

To that extent, introduce PHY support in netdevsim. The main goal (for now) is not to be able to test PHYlib, but these phy-specific netlink interfaces.

These netdevsim PHYs use a custom phy_driver that relies on re-implementing the phy_driver callbacks. In other words, this is not a PHY driver that relies on mdio emulation, and will not work with any of the genphy helpers.

The debugfs API for PHY creation and deletion works as follows :

PHY device creation :

echo $ID > /sys/kernel/debug/netdevsim/netdevsimXXX/ports/YY/phy_add

if $ID is 0, then the PHY parent will be the netdev corresponding to the port's netdev. The first PHY that is added with the netdev as a parent will be attached to the netdev.

if $ID > 0, the index must correspond to a previously added PHY. This allows creating any arbitrary tree of PHYs.

Upon PHY addition, a phyXX directory will be created, XX being the phyindex of the PHY in the topology:

[...]/ports/YY/phyXX/

This directory contains a "link" file, allowing to toggle the virtual PHY's link state.

One can then list the PHYs with "ethtool --show-phys ethX".

Signed-off-by: Maxime Chevallier maxime.chevallier@bootlin.com

drivers/net/netdevsim/Makefile | 4 + drivers/net/netdevsim/dev.c | 2 + drivers/net/netdevsim/netdev.c | 8 + drivers/net/netdevsim/netdevsim.h | 25 ++ drivers/net/netdevsim/phy.c | 398 ++++++++++++++++++++++++++++++ 5 files changed, 437 insertions(+) create mode 100644 drivers/net/netdevsim/phy.c

diff --git a/drivers/net/netdevsim/Makefile b/drivers/net/netdevsim/Makefile index f8de93bc5f5b..49f4c515e5e3 100644 --- a/drivers/net/netdevsim/Makefile +++ b/drivers/net/netdevsim/Makefile @@ -21,3 +21,7 @@ endif ifneq ($(CONFIG_MACSEC),) netdevsim-objs += macsec.o endif

+ifneq ($(CONFIG_PHYLIB),) +netdevsim-objs += phy.o +endif diff --git a/drivers/net/netdevsim/dev.c b/drivers/net/netdevsim/dev.c index b3647691060c..1ebb4f5b3bdd 100644 --- a/drivers/net/netdevsim/dev.c +++ b/drivers/net/netdevsim/dev.c @@ -1510,6 +1510,7 @@ static int nsim_dev_reload_create(struct nsim_dev *nsim_dev, devlink = priv_to_devlink(nsim_dev); nsim_dev = devlink_priv(devlink); INIT_LIST_HEAD(&nsim_dev->port_list);

• INIT_LIST_HEAD(&nsim_dev->phy_list); nsim_dev->fw_update_status = true; nsim_dev->fw_update_overwrite_mask = 0;

@@ -1583,6 +1584,7 @@ int nsim_drv_probe(struct nsim_bus_dev *nsim_bus_dev) nsim_dev->switch_id.id_len = sizeof(nsim_dev->switch_id.id); get_random_bytes(nsim_dev->switch_id.id, nsim_dev->switch_id.id_len); INIT_LIST_HEAD(&nsim_dev->port_list);

• INIT_LIST_HEAD(&nsim_dev->phy_list); nsim_dev->fw_update_status = true; nsim_dev->fw_update_overwrite_mask = 0; nsim_dev->max_macs = NSIM_DEV_MAX_MACS_DEFAULT;

diff --git a/drivers/net/netdevsim/netdev.c b/drivers/net/netdevsim/netdev.c index e36d3e846c2d..ff891536f691 100644 --- a/drivers/net/netdevsim/netdev.c +++ b/drivers/net/netdevsim/netdev.c @@ -952,6 +952,7 @@ static int nsim_init_netdevsim(struct netdevsim *ns) nsim_macsec_init(ns); nsim_ipsec_init(ns);

• nsim_phy_init(ns);

err = register_netdevice(ns->netdev); if (err) @@ -968,6 +969,7 @@ static int nsim_init_netdevsim(struct netdevsim *ns) return 0; err_ipsec_teardown:

• nsim_phy_teardown(ns); nsim_ipsec_teardown(ns); nsim_macsec_teardown(ns); nsim_bpf_uninit(ns);

@@ -1058,6 +1060,7 @@ void nsim_destroy(struct netdevsim *ns) RCU_INIT_POINTER(ns->peer, NULL); unregister_netdevice(dev); if (nsim_dev_port_is_pf(ns->nsim_dev_port)) {

• nsim_phy_teardown(ns);
  

  nsim_macsec_teardown(ns); nsim_ipsec_teardown(ns); nsim_bpf_uninit(ns);

@@ -1098,6 +1101,10 @@ static int __init nsim_module_init(void) { int err;

• err = nsim_phy_drv_register();
• if (err)

• return err;
  

• err = nsim_dev_init(); if (err) return err;

@@ -1124,6 +1131,7 @@ static void __exit nsim_module_exit(void) rtnl_link_unregister(&nsim_link_ops); nsim_bus_exit(); nsim_dev_exit();

• nsim_phy_drv_unregister();

} module_init(nsim_module_init); diff --git a/drivers/net/netdevsim/netdevsim.h b/drivers/net/netdevsim/netdevsim.h index 809dd29fc5fe..c73d16e67a3c 100644 --- a/drivers/net/netdevsim/netdevsim.h +++ b/drivers/net/netdevsim/netdevsim.h @@ -314,6 +314,7 @@ struct nsim_dev { struct list_head bpf_bound_maps; struct netdev_phys_item_id switch_id; struct list_head port_list;

• struct list_head phy_list; bool fw_update_status; u32 fw_update_overwrite_mask; u32 max_macs;

@@ -419,6 +420,30 @@ static inline void nsim_macsec_teardown(struct netdevsim *ns) } #endif +#if IS_ENABLED(CONFIG_PHYLIB) +void nsim_phy_init(struct netdevsim *ns); +void nsim_phy_teardown(struct netdevsim *dev); +int nsim_phy_drv_register(void); +void nsim_phy_drv_unregister(void); +#else +static inline void nsim_phy_init(struct netdevsim *ns) +{ +}

+static inline void nsim_phy_teardown(struct netdevsim *ns);

Meh... that's why this fails, stray ';' that slept through the cracks when building netdevsim with CONFIG_PHYLIB=n ...

I'll address that,

Maxime