linux-kernel - Re: [RFC PATCH net-next v2 01/10] net: phy: Introduce ethernet link topology representation

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Message-ID: <20231123143408.3cae1b04@device.home>
Date:   Thu, 23 Nov 2023 14:34:08 +0100
From:   Maxime Chevallier <maxime.chevallier@...tlin.com>
To:     Andrew Lunn <andrew@...n.ch>
Cc:     davem@...emloft.net, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, thomas.petazzoni@...tlin.com,
        Jakub Kicinski <kuba@...nel.org>,
        Eric Dumazet <edumazet@...gle.com>,
        Paolo Abeni <pabeni@...hat.com>,
        Russell King <linux@...linux.org.uk>,
        linux-arm-kernel@...ts.infradead.org,
        Christophe Leroy <christophe.leroy@...roup.eu>,
        Herve Codina <herve.codina@...tlin.com>,
        Florian Fainelli <f.fainelli@...il.com>,
        Heiner Kallweit <hkallweit1@...il.com>,
        Vladimir Oltean <vladimir.oltean@....com>,
        Köry Maincent <kory.maincent@...tlin.com>,
        Jesse Brandeburg <jesse.brandeburg@...el.com>
Subject: Re: [RFC PATCH net-next v2 01/10] net: phy: Introduce ethernet link
 topology representation

Hello Andrew,

On Tue, 21 Nov 2023 01:24:47 +0100
Andrew Lunn <andrew@...n.ch> wrote:

> > +int link_topo_add_phy(struct link_topology *lt, struct phy_device *phy,
> > +		      enum phy_upstream upt, void *upstream)
> > +{
> > +	ret = xa_alloc_cyclic(&lt->phys, &phy->phyindex, pdn, xa_limit_32b,
> > +			      &lt->next_phy_index, GFP_KERNEL);
> > +	if (ret)
> > +		goto err;
> > +
> > +	return 0;  
> 
> It looks like that could be just return xa_alloc_cyclic(...);

Indeed, nice catch

> 
> > diff --git a/include/linux/link_topology.h b/include/linux/link_topology.h  
> 
> I think this filename is too generic. Maybe phy_link_topology.h, or
> move it into include/net.
> 
> > +struct phy_device *link_topo_get_phy(struct link_topology *lt, int phyindex);
> > +int link_topo_add_phy(struct link_topology *lt, struct phy_device *phy,
> > +		      enum phy_upstream upt, void *upstream);
> > +
> > +void link_topo_del_phy(struct link_topology *lt, struct phy_device *phy);  
> 
> What is the locking for these functions? Are you assuming RTNL? Maybe
> add ASSERT_RTNL(); into them to make this clear.

Indeed I assume it, I'll add an assert and document that clearly then.

> 
> > diff --git a/include/linux/link_topology_core.h b/include/linux/link_topology_core.h  
> 
> Again, i think this filename is too generic.
> 
> > diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
> > index a16c9cc063fe..7021a0d3d982 100644
> > --- a/include/linux/netdevice.h
> > +++ b/include/linux/netdevice.h
> > @@ -40,7 +40,6 @@
> >  #include <net/dcbnl.h>
> >  #endif
> >  #include <net/netprio_cgroup.h>
> > -
> >  #include <linux/netdev_features.h>  
> 
> Whitespace change.
> 
> >  #include <linux/neighbour.h>
> >  #include <uapi/linux/netdevice.h>
> > @@ -52,6 +51,7 @@
> >  #include <net/net_trackers.h>
> >  #include <net/net_debug.h>
> >  #include <net/dropreason-core.h>
> > +#include <linux/link_topology_core.h>
> >  
> >  struct netpoll_info;
> >  struct device;
> > @@ -2405,6 +2405,7 @@ struct net_device {
> >  #if IS_ENABLED(CONFIG_CGROUP_NET_PRIO)
> >  	struct netprio_map __rcu *priomap;
> >  #endif
> > +	struct link_topology	link_topo;
> >  	struct phy_device	*phydev;
> >  	struct sfp_bus		*sfp_bus;
> >  	struct lock_class_key	*qdisc_tx_busylock;
> > diff --git a/include/linux/phy.h b/include/linux/phy.h
> > index 3cc52826f18e..d698180b1df0 100644
> > --- a/include/linux/phy.h
> > +++ b/include/linux/phy.h
> > @@ -543,6 +543,8 @@ struct macsec_ops;
> >   * @drv: Pointer to the driver for this PHY instance
> >   * @devlink: Create a link between phy dev and mac dev, if the external phy
> >   *           used by current mac interface is managed by another mac interface.
> > + * @phyindex: Unique id across the phy's parent tree of phys to address the PHY
> > + *	      from userspace, similar to ifindex. It's never recycled.
> >   * @phy_id: UID for this device found during discovery
> >   * @c45_ids: 802.3-c45 Device Identifiers if is_c45.
> >   * @is_c45:  Set to true if this PHY uses clause 45 addressing.
> > @@ -640,6 +642,7 @@ struct phy_device {
> >  
> >  	struct device_link *devlink;
> >  
> > +	int phyindex;  
> 
> Is this int, or unsigned int? Is a negative value possible and legal?

You're right this should be unsigned. I've also missed properly
documenting correct values and their meaning (like phyindex 0 would be
no index assigned).

> 
> > +enum phy_upstream {
> > +	PHY_UPSTREAM_MAC,
> > +	PHY_UPSTREAM_SFP,
> > +	PHY_UPSTREAM_PHY,
> > +};  
> 
> Please document what these actually mean.

I'll do this as well.

Thank you for reviewing,

Maxime

> 
>        Andrew