linux-kernel - Re: [RFC PATCH net-next 1/3] net: phy: don't bind genphy in phy_attach_direct if the specific driver defers probe

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Date:   Fri, 3 Sep 2021 01:02:06 +0200
From:   Andrew Lunn <andrew@...n.ch>
To:     Vladimir Oltean <olteanv@...il.com>
Cc:     "Russell King (Oracle)" <linux@...linux.org.uk>,
        Florian Fainelli <f.fainelli@...il.com>,
        Vladimir Oltean <vladimir.oltean@....com>,
        netdev@...r.kernel.org,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Heiner Kallweit <hkallweit1@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Vivien Didelot <vivien.didelot@...il.com>,
        linux-kernel@...r.kernel.org,
        Linus Walleij <linus.walleij@...aro.org>,
        Alvin Šipraga <alsi@...g-olufsen.dk>,
        ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
        kernel-team <kernel-team@...roid.com>,
        Len Brown <lenb@...nel.org>
Subject: Re: [RFC PATCH net-next 1/3] net: phy: don't bind genphy in
 phy_attach_direct if the specific driver defers probe

> > Note that phylink_destroy() is documented as:
> >
> >  * Note: the rtnl lock must not be held when calling this function.
> >

...

> 
> Any other issues besides needing to take rtnl_mutex top-level when
> calling phylink_destroy?

We should try to keep phylink_create and phylink_destroy symmetrical:

/**
 * phylink_create() - create a phylink instance
 * @config: a pointer to the target &struct phylink_config
 * @fwnode: a pointer to a &struct fwnode_handle describing the network
 *      interface
 * @iface: the desired link mode defined by &typedef phy_interface_t
 * @mac_ops: a pointer to a &struct phylink_mac_ops for the MAC.
 *
 * Create a new phylink instance, and parse the link parameters found in @np.
 * This will parse in-band modes, fixed-link or SFP configuration.
 *
 * Note: the rtnl lock must not be held when calling this function.

Having different locking requirements will catch people out.

Interestingly, there is no ASSERT_NO_RTNL(). Maybe we should add such
a macro.

    Andrew