linux-kernel - Re: [PATCH net-next v3 07/47] net: phy: Add support for rate adaptation

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Date:   Sat, 16 Jul 2022 21:39:29 +0200
From:   Andrew Lunn <andrew@...n.ch>
To:     Sean Anderson <sean.anderson@...o.com>
Cc:     "David S . Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Madalin Bucur <madalin.bucur@....com>, netdev@...r.kernel.org,
        Paolo Abeni <pabeni@...hat.com>,
        Eric Dumazet <edumazet@...gle.com>,
        linux-arm-kernel@...ts.infradead.org,
        Russell King <linux@...linux.org.uk>,
        linux-kernel@...r.kernel.org,
        Alexandru Marginean <alexandru.marginean@....com>,
        Heiner Kallweit <hkallweit1@...il.com>,
        Vladimir Oltean <olteanv@...il.com>
Subject: Re: [PATCH net-next v3 07/47] net: phy: Add support for rate
 adaptation

>  drivers/net/phy/phy.c | 21 +++++++++++++++++++++
>  include/linux/phy.h   | 38 ++++++++++++++++++++++++++++++++++++++
>  2 files changed, 59 insertions(+)
> 
> diff --git a/drivers/net/phy/phy.c b/drivers/net/phy/phy.c
> index 8d3ee3a6495b..cf4a8b055a42 100644
> --- a/drivers/net/phy/phy.c
> +++ b/drivers/net/phy/phy.c
> @@ -114,6 +114,27 @@ void phy_print_status(struct phy_device *phydev)
>  }
>  EXPORT_SYMBOL(phy_print_status);
>  
> +/**
> + * phy_get_rate_adaptation - determine if rate adaptation is supported
> + * @phydev: The phy device to return rate adaptation for
> + * @iface: The interface mode to use
> + *
> + * This determines the type of rate adaptation (if any) that @phy supports
> + * using @iface. @iface may be %PHY_INTERFACE_MODE_NA to determine if any
> + * interface supports rate adaptation.
> + *
> + * Return: The type of rate adaptation @phy supports for @iface, or
> + *         %RATE_ADAPT_NONE.
> + */
> +enum rate_adaptation phy_get_rate_adaptation(struct phy_device *phydev,
> +					     phy_interface_t iface)
> +{
> +	if (phydev->drv->get_rate_adaptation)
> +		return phydev->drv->get_rate_adaptation(phydev, iface);

It is normal that any call into the driver is performed with the
phydev->lock held.

>  #define PHY_INIT_TIMEOUT	100000
>  #define PHY_FORCE_TIMEOUT	10
> @@ -570,6 +588,7 @@ struct macsec_ops;
>   * @lp_advertising: Current link partner advertised linkmodes
>   * @eee_broken_modes: Energy efficient ethernet modes which should be prohibited
>   * @autoneg: Flag autoneg being used
> + * @rate_adaptation: Current rate adaptation mode
>   * @link: Current link state
>   * @autoneg_complete: Flag auto negotiation of the link has completed
>   * @mdix: Current crossover
> @@ -637,6 +656,8 @@ struct phy_device {
>  	unsigned irq_suspended:1;
>  	unsigned irq_rerun:1;
>  
> +	enum rate_adaptation rate_adaptation;

It is not clear what the locking is on this member. Is it only safe to
access it during the adjust_link callback, when it is guaranteed that
the phydev->lock is held, so the value is consistent? Or is the MAC
allowed to access this at other times?

	Andrew