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Date: Tue, 30 Apr 2024 23:29:37 +0200
From: Heiner Kallweit <hkallweit1@...il.com>
To: Maxime Chevallier <maxime.chevallier@...tlin.com>
Cc: davem@...emloft.net, 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 30.04.2024 13:57, Maxime Chevallier wrote:
> Hello Heiner,
>
> On Tue, 30 Apr 2024 10:17:31 +0200
> Heiner Kallweit <hkallweit1@...il.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@...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 */
>>
>
To go a little bit more into detail:
phy_link_topo_create() and phy_link_topo_destroy() are used in net/core/dev.c
only. Do you expect them to be ever used by other callers?
If not, their functionality could be moved to net/core/dev.c.
Supposedly guarded by IS_ENABLED(CONFIG_PHYLIB), alternatively a new config
symbol for link_topo support.
To get rid of the dependency you could also lazy-inizialize
netdev->link_topo. For this phy_link_topo_add_phy() would have
to take the netdev as first argument, not the topo.
Then the first call to phy_link_topo_add_phy() would initialize
netdev->link_topo.
I think functions like phy_link_topo_get_phy() should also check for
topo != NULL first, maybe combined with a WARN_ON().
They are exported and you have no control over its use.
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