linux-kernel - Re: [net-next PATCH v4 03/11] net: pcs: Add subsystem

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Message-ID: <a7edb7e8-37ac-45ae-b5c7-2c9034dce4d7@quicinc.com>
Date: Wed, 21 May 2025 20:50:48 +0800
From: Lei Wei <quic_leiwei@...cinc.com>
To: Sean Anderson <sean.anderson@...ux.dev>, <netdev@...r.kernel.org>,
        Andrew
 Lunn <andrew+netdev@...n.ch>,
        "David S . Miller" <davem@...emloft.net>,
        Eric
 Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni
	<pabeni@...hat.com>, Russell King <linux@...linux.org.uk>
CC: <upstream@...oha.com>, Kory Maincent <kory.maincent@...tlin.com>,
        Simon
 Horman <horms@...nel.org>,
        Christian Marangi <ansuelsmth@...il.com>,
        <linux-kernel@...r.kernel.org>, Heiner Kallweit <hkallweit1@...il.com>,
        Jonathan Corbet <corbet@....net>, <linux-doc@...r.kernel.org>
Subject: Re: [net-next PATCH v4 03/11] net: pcs: Add subsystem



On 5/20/2025 1:43 AM, Sean Anderson wrote:
> On 5/14/25 12:22, Lei Wei wrote:
>>
>>
>> On 5/13/2025 12:10 AM, Sean Anderson wrote:
>>> +/**
>>> + * pcs_register_full() - register a new PCS
>>> + * @dev: The device requesting the PCS
>>> + * @fwnode: The PCS's firmware node; typically @dev.fwnode
>>> + * @pcs: The PCS to register
>>> + *
>>> + * Registers a new PCS which can be attached to a phylink.
>>> + *
>>> + * Return: 0 on success, or -errno on error
>>> + */
>>> +int pcs_register_full(struct device *dev, struct fwnode_handle *fwnode,
>>> +              struct phylink_pcs *pcs)
>>> +{
>>> +    struct pcs_wrapper *wrapper;
>>> +
>>> +    if (!dev || !pcs->ops)
>>> +        return -EINVAL;
>>> +
>>> +    if (!pcs->ops->pcs_an_restart || !pcs->ops->pcs_config ||
>>> +        !pcs->ops->pcs_get_state)
>>> +        return -EINVAL;
>>> +
>>> +    wrapper = kzalloc(sizeof(*wrapper), GFP_KERNEL);
>>> +    if (!wrapper)
>>> +        return -ENOMEM;
>>
>> How about the case where pcs is removed and then comes back again? Should we find the original wrapper and attach it to pcs again instead of creating a new wrapper?
> 
> When the PCS is removed the old wrapper is removed from pcs_wrappers, so
> it can no longer be looked up any more. I think trying to save/restore
> the wrapper would be much more trouble than it's worth.
> 

In the case where Ethernet is not removed but PCS is removed and then
comes back (when the sysfs unbind followed by bind method is used),
it will not work because the Ethernet probe will not be initiated again, 
to call "pcs_get" again to obtain the new wrapper, it would still hold 
the old wrapper.

> --Sean