[PATCH net-next] net: emaclite: Add error handling for of_address_ and phy read functions

[Jakub Kicinski]

On Tue, 3 Nov 2020 19:01:05 +0530 Radhey Shyam Pandey wrote:
> From: Shravya Kumbham <shravya.kumbham at xilinx.com>
> 
> Add ret variable, conditions to check the return value and it's error
> path for of_address_to_resource() and phy_read() functions.
> 
> Addresses-Coverity: Event check_return value.
> Signed-off-by: Shravya Kumbham <shravya.kumbham at xilinx.com>
> Signed-off-by: Radhey Shyam Pandey <radhey.shyam.pandey at xilinx.com>

Any reason not to apply this to net as a fix?

> diff --git a/drivers/net/ethernet/xilinx/xilinx_emaclite.c b/drivers/net/ethernet/xilinx/xilinx_emaclite.c
> index 0c26f5b..fc5ccd1 100644
> --- a/drivers/net/ethernet/xilinx/xilinx_emaclite.c
> +++ b/drivers/net/ethernet/xilinx/xilinx_emaclite.c
> @@ -820,7 +820,7 @@ static int xemaclite_mdio_write(struct mii_bus *bus, int phy_id, int reg,
>  static int xemaclite_mdio_setup(struct net_local *lp, struct device *dev)
>  {
>  	struct mii_bus *bus;
> -	int rc;
> +	int rc, ret;
>  	struct resource res;
>  	struct device_node *np = of_get_parent(lp->phy_node);
>  	struct device_node *npp;
> @@ -834,7 +834,13 @@ static int xemaclite_mdio_setup(struct net_local *lp, struct device *dev)
>  	}
>  	npp = of_get_parent(np);
>  
> -	of_address_to_resource(npp, 0, &res);
> +	ret = of_address_to_resource(npp, 0, &res);
> +	if (ret) {
> +		dev_err(dev, "%s resource error!\n",
> +			dev->of_node->full_name);
> +		of_node_put(lp->phy_node);

I'm always confused by the of_* refcounting. Why do you need to put
phy_node here, and nowhere else in this function?

> +		return ret;
> +	}

>  		/* Restart auto negotiation */
>  		bmcr = phy_read(lp->phy_dev, MII_BMCR);
> +		if (bmcr < 0) {
> +			dev_err(&lp->ndev->dev, "phy_read failed\n");
> +			phy_disconnect(lp->phy_dev);
> +			lp->phy_dev = NULL;
> +
> +			return bmcr;
> +		}
>  		bmcr |= (BMCR_ANENABLE | BMCR_ANRESTART);
>  		phy_write(lp->phy_dev, MII_BMCR, bmcr);

Does it really make much sense to validate the return value of
phy_read() but not check any errors from phy_write()s?