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Date: Tue, 30 Apr 2024 13:57:34 +0200
From: Maxime Chevallier <maxime.chevallier@bootlin.com>
To: Heiner Kallweit <hkallweit1@gmail.com>
Cc: davem@davemloft.net, netdev@vger.kernel.org,
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Subject: Re: [PATCH net-next] net: phy: Don't conditionally compile the
 phy_link_topology creation
Message-ID: <20240430135734.503f51a2@device-28.home>
In-Reply-To: <1ed5b8cb-c79b-44b9-8dbe-f78d7505b3b4@gmail.com>
References: <20240429131008.439231-1-maxime.chevallier@bootlin.com>
	<1ed5b8cb-c79b-44b9-8dbe-f78d7505b3b4@gmail.com>
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Hello Heiner,

On Tue, 30 Apr 2024 10:17:31 +0200
Heiner Kallweit <hkallweit1@gmail.com> wrote:

> On 29.04.2024 15:10, Maxime Chevallier wrote:
> > The core of the phy_link_topology isn't directly tied to phylib, and at
> > the moment it's initialized, phylib might not be loaded yet. Move the
> > initialization of the topology to the phy_link_topology_core header,
> > which contains the bare minimum so that we can initialize it at netdev
> > creation.
> >   
> 
> The change fixes the issue for me, but according to my personal taste
> the code isn't intuitive and still error-prone. Also there's no good
> reason to inline a function like phy_link_topo_create() and make it
> publicly available. Do you expect it to be ever used outside net core?
> In general it may make sense to add a config symbol for the topology
> extension, there seem to be very few, specialized use cases for it.

I think I'm missing the point here then. Do you mean adding a Kconfig
option to explicitely turn phy_link_topology on ? or build it as a
dedicated kernel module ?

Or do you see something such as "if phylib is M or Y, then build the
topology stuff and make sure it's allocated when a netdev gets created
?"

Thanks,

Maxime

> 
> > Signed-off-by: Maxime Chevallier <maxime.chevallier@bootlin.com>
> > Closes: https://lore.kernel.org/netdev/2e11b89d-100f-49e7-9c9a-834cc0b82f97@gmail.com/
> > Closes: https://lore.kernel.org/netdev/20240409201553.GA4124869@dev-arch.thelio-3990X/
> > ---
> >  drivers/net/phy/phy_link_topology.c    | 23 --------------------
> >  include/linux/phy_link_topology.h      |  5 -----
> >  include/linux/phy_link_topology_core.h | 30 +++++++++++++++++---------
> >  3 files changed, 20 insertions(+), 38 deletions(-)
> > 
> > diff --git a/drivers/net/phy/phy_link_topology.c b/drivers/net/phy/phy_link_topology.c
> > index 985941c5c558..960aedd73308 100644
> > --- a/drivers/net/phy/phy_link_topology.c
> > +++ b/drivers/net/phy/phy_link_topology.c
> > @@ -12,29 +12,6 @@
> >  #include <linux/rtnetlink.h>
> >  #include <linux/xarray.h>
> >  
> > -struct phy_link_topology *phy_link_topo_create(struct net_device *dev)
> > -{
> > -	struct phy_link_topology *topo;
> > -
> > -	topo = kzalloc(sizeof(*topo), GFP_KERNEL);
> > -	if (!topo)
> > -		return ERR_PTR(-ENOMEM);
> > -
> > -	xa_init_flags(&topo->phys, XA_FLAGS_ALLOC1);
> > -	topo->next_phy_index = 1;
> > -
> > -	return topo;
> > -}
> > -
> > -void phy_link_topo_destroy(struct phy_link_topology *topo)
> > -{
> > -	if (!topo)
> > -		return;
> > -
> > -	xa_destroy(&topo->phys);
> > -	kfree(topo);
> > -}
> > -
> >  int phy_link_topo_add_phy(struct phy_link_topology *topo,
> >  			  struct phy_device *phy,
> >  			  enum phy_upstream upt, void *upstream)
> > diff --git a/include/linux/phy_link_topology.h b/include/linux/phy_link_topology.h
> > index 6b79feb607e7..ad72d7881257 100644
> > --- a/include/linux/phy_link_topology.h
> > +++ b/include/linux/phy_link_topology.h
> > @@ -32,11 +32,6 @@ struct phy_device_node {
> >  	struct phy_device *phy;
> >  };
> >  
> > -struct phy_link_topology {
> > -	struct xarray phys;
> > -	u32 next_phy_index;
> > -};
> > -
> >  static inline struct phy_device *
> >  phy_link_topo_get_phy(struct phy_link_topology *topo, u32 phyindex)
> >  {
> > diff --git a/include/linux/phy_link_topology_core.h b/include/linux/phy_link_topology_core.h
> > index 0a6479055745..0116ec49cd1b 100644
> > --- a/include/linux/phy_link_topology_core.h
> > +++ b/include/linux/phy_link_topology_core.h
> > @@ -2,24 +2,34 @@
> >  #ifndef __PHY_LINK_TOPOLOGY_CORE_H
> >  #define __PHY_LINK_TOPOLOGY_CORE_H
> >  
> > -struct phy_link_topology;
> > +#include <linux/xarray.h>
> >  
> > -#if IS_REACHABLE(CONFIG_PHYLIB)
> > -
> > -struct phy_link_topology *phy_link_topo_create(struct net_device *dev);
> > -void phy_link_topo_destroy(struct phy_link_topology *topo);
> > -
> > -#else
> > +struct phy_link_topology {
> > +	struct xarray phys;
> > +	u32 next_phy_index;
> > +};
> >  
> >  static inline struct phy_link_topology *phy_link_topo_create(struct net_device *dev)
> >  {
> > -	return NULL;
> > +	struct phy_link_topology *topo;
> > +
> > +	topo = kzalloc(sizeof(*topo), GFP_KERNEL);
> > +	if (!topo)
> > +		return ERR_PTR(-ENOMEM);
> > +
> > +	xa_init_flags(&topo->phys, XA_FLAGS_ALLOC1);
> > +	topo->next_phy_index = 1;
> > +
> > +	return topo;
> >  }
> >  
> >  static inline void phy_link_topo_destroy(struct phy_link_topology *topo)
> >  {
> > -}
> > +	if (!topo)
> > +		return;
> >  
> > -#endif
> > +	xa_destroy(&topo->phys);
> > +	kfree(topo);
> > +}
> >  
> >  #endif /* __PHY_LINK_TOPOLOGY_CORE_H */  
>