netdev - Re: [PATCH net-next] net: phy: Don't conditionally compile the phy_link

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Message-ID: <1ed5b8cb-c79b-44b9-8dbe-f78d7505b3b4@gmail.com>
Date: Tue, 30 Apr 2024 10:17:31 +0200
From: Heiner Kallweit <hkallweit1@...il.com>
To: Maxime Chevallier <maxime.chevallier@...tlin.com>, davem@...emloft.net
Cc: netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
 thomas.petazzoni@...tlin.com, Andrew Lunn <andrew@...n.ch>,
 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>,
 Vladimir Oltean <vladimir.oltean@....com>,
 Köry Maincent <kory.maincent@...tlin.com>,
 Jesse Brandeburg <jesse.brandeburg@...el.com>, Marek Behún
 <kabel@...nel.org>, Piergiorgio Beruto <piergiorgio.beruto@...il.com>,
 Oleksij Rempel <o.rempel@...gutronix.de>,
 Nicolò Veronese <nicveronese@...il.com>,
 Simon Horman <horms@...nel.org>, mwojtas@...omium.org,
 Nathan Chancellor <nathan@...nel.org>, Antoine Tenart <atenart@...nel.org>
Subject: Re: [PATCH net-next] net: phy: Don't conditionally compile the
 phy_link_topology creation

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.

> Signed-off-by: Maxime Chevallier <maxime.chevallier@...tlin.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 */