linux-kernel - Re: [PATCH] usb: dwc3: drd: Avoid error when extcon is missing

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Message-ID: <20201211144936.GT4077@smile.fi.intel.com>
Date:   Fri, 11 Dec 2020 16:49:36 +0200
From:   Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:     Sam Protsenko <semen.protsenko@...aro.org>
Cc:     linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org,
        Felipe Balbi <balbi@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        John Stultz <john.stultz@...aro.org>
Subject: Re: [PATCH] usb: dwc3: drd: Avoid error when extcon is missing

On Fri, Dec 11, 2020 at 04:24:21PM +0200, Sam Protsenko wrote:
> If "port" node is missing in PHY controller node, dwc3_get_extcon()
> isn't able to find extcon device. This is perfectly fine in case when
> "usb-role-switch" or OTG is used, but next misleading error message is
> printed in that case, from of_graph_get_remote_node():
> 
>     OF: graph: no port node found in /phy@...4abcd
> 
> Avoid printing that message by checking if port node exists in PHY node
> before calling of_graph_get_remote_node().

So, this has to be v2...
Anyway, see below.

...

>  static struct extcon_dev *dwc3_get_extcon(struct dwc3 *dwc)
>  {
>  	struct device *dev = dwc->dev;
> -	struct device_node *np_phy, *np_conn;
> -	struct extcon_dev *edev;
> +	struct device_node *np_phy;
> +	struct extcon_dev *edev = NULL;
>  	const char *name;
>  
>  	if (device_property_read_bool(dev, "extcon"))
> @@ -462,15 +462,22 @@ static struct extcon_dev *dwc3_get_extcon(struct dwc3 *dwc)
>  		return edev;
>  	}
>  
> +	/*
> +	 * Try to get extcon device from USB PHY controller's "port" node.
> +	 * Check if it has the "port" node first, to avoid printing the error
> +	 * message from underlying code, as it's a valid case: extcon device
> +	 * (and "port" node) may be missing in case of "usb-role-switch" or OTG
> +	 * mode.
> +	 */
>  	np_phy = of_parse_phandle(dev->of_node, "phys", 0);
> -	np_conn = of_graph_get_remote_node(np_phy, -1, -1);
> +	if (of_graph_is_present(np_phy)) {
> +		struct device_node *np_conn;
>  
> -	if (np_conn)
> -		edev = extcon_find_edev_by_node(np_conn);
> -	else
> -		edev = NULL;
> -
> -	of_node_put(np_conn);
> +		np_conn = of_graph_get_remote_node(np_phy, -1, -1);
> +		if (np_conn)
> +			edev = extcon_find_edev_by_node(np_conn);
> +		of_node_put(np_conn);
> +	}
>  	of_node_put(np_phy);
>  
>  	return edev;


Why not do it slightly different, i.e.

-	np_conn = of_graph_get_remote_node(np_phy, -1, -1);
+	if (of_graph_is_present(np_phy))
+		np_conn = of_graph_get_remote_node(np_phy, -1, -1);
+	else
+		np_conn = NULL;

?

-- 
With Best Regards,
Andy Shevchenko