netdev - Re: [PATCH] net: qcom/emac: grab a reference to the phydev on ACPI systems

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Date:   Tue, 10 Jan 2017 09:45:27 +0100
From:   Johan Hovold <johan@...nel.org>
To:     Timur Tabi <timur@...eaurora.org>
Cc:     David Miller <davem@...emloft.net>, johan@...nel.org,
        netdev@...r.kernel.org
Subject: Re: [PATCH] net: qcom/emac: grab a reference to the phydev on ACPI
 systems

On Mon, Jan 09, 2017 at 05:52:06PM -0600, Timur Tabi wrote:
> Commit 6ffe1c4cd0a7 ("net: qcom/emac: fix of_node and phydev leaks")
> fixed the problem with reference leaks on phydev, but the fix is
> device-tree specific.  When the driver unloads, the reference is
> dropped only on DT systems.
> 
> Instead, it's cleaner if up grab an reference on ACPI systems.
> When the driver unloads, we can drop the reference without having
> to check whether we're on a DT system.
> 
> Signed-off-by: Timur Tabi <timur@...eaurora.org>
> ---
>  drivers/net/ethernet/qualcomm/emac/emac-phy.c | 6 ++++++
>  drivers/net/ethernet/qualcomm/emac/emac.c     | 6 ++----
>  2 files changed, 8 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/net/ethernet/qualcomm/emac/emac-phy.c b/drivers/net/ethernet/qualcomm/emac/emac-phy.c
> index 99a14df..af485f1 100644
> --- a/drivers/net/ethernet/qualcomm/emac/emac-phy.c
> +++ b/drivers/net/ethernet/qualcomm/emac/emac-phy.c
> @@ -201,6 +201,12 @@ int emac_phy_config(struct platform_device *pdev, struct emac_adapter *adpt)
>  		else
>  			adpt->phydev = mdiobus_get_phy(mii_bus, phy_addr);
>  
> +		/* of_phy_find_device() claims a reference to the phydev,
> +		 * so we do that here manually as well. When the driver
> +		 * unloads, it can unilaterally drops the reference
> +		 * without worrying about ACPI vs DT.
> +		 */
> +		get_device(&adpt->phydev->mdio.dev);

But you cannot do this unconditionally as adpt->phydev can be NULL here.

Looks good to me otherwise.

Thanks,
Johan