Re: [PATCH 2/3] usb: chipidea: host: let the hcd know's parent device node

On Fri, Mar 04, 2016 at 03:17:30AM +0100, Andrew Lunn wrote:

quoted

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diff --git a/drivers/usb/chipidea/host.c b/drivers/usb/chipidea/host.c
index 053bac9..55120ef 100644
--- a/drivers/usb/chipidea/host.c
+++ b/drivers/usb/chipidea/host.c

@@ -109,15 +109,25 @@ static int host_start(struct ci_hdrc *ci)
 	struct ehci_hcd *ehci;
 	struct ehci_ci_priv *priv;
 	int ret;
+	struct device *dev = ci->dev;
 
-	if (usb_disabled())
+	if (usb_disabled() || !dev)
 		return -ENODEV;
 
-	hcd = usb_create_hcd(&ci_ehci_hc_driver, ci->dev, dev_name(ci->dev));
+	/*
+	 * USB Core will try to get child node under roothub,
+	 * but chipidea core has no of_node, and the child node
+	 * for controller is located at glue layer's node which
+	 * is chipidea core's parent.
+	 */
+	if (dev->parent && dev->parent->of_node)
+		dev->of_node = dev->parent->of_node;

Is this a good idea? Two devices with the same of_node?

This is only for chipidea driver whose host controller device
doesn't have entry at dts, but other host controller driver which
supports device tree should have its entry at dts.

quoted

I know the networking code assumes of_node values are unique, and uses
it to find a device. Are you 100% sure the USB code does not make this
assumption.

The controller device is the root for USB device, the common
USB code will not touch its glue layer device (controller's parent).

I'm just thinking about code like:

of_find_spi_master_by_node(), of_find_net_device_by_node(),
of_find_backlight_by_node(), etc.

If somebody was to implement an of_find_usb_host_by_node() are you
100% sure the right node will be found? This seems like a bug waiting
to happen.

Yes, almost 100% sure it is ok since the common USB code will never use
its root's parent node to match or get something.

-- 

Best Regards,
Peter Chen
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