Re: [PATCH v3 1/1] USB: core: let USB device know device node

On Fri, Jan 15, 2016 at 12:30:41PM -0500, Alan Stern wrote:

On Fri, 15 Jan 2016, Philipp Zabel wrote:

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+- reg: the port number which this device is connecting to.

Should it be noted here that the port number range is 1-255?

Actually the range is 1 - 31 (defined by USB_MAXCHILDREN set in 
include/uapi/linux/usb/ch11.h).

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@@ -502,11 +503,14 @@ struct usb_device *usb_alloc_dev(struct usb_device *parent,
 	dev->connect_time = jiffies;
 	dev->active_duration = -jiffies;
 #endif
-	if (root_hub)	/* Root hub always ok [and always wired] */
+	if (root_hub) {	/* Root hub always ok [and always wired] */
 		dev->authorized = 1;
-	else {
+		dev->of_node = bus->controller->of_node;

Why can't the root_hub reuse dev->dev.of_node?

Indeed, there's no need to add an .of_node field to struct usb_device, 
since the embedded struct device already contains an .of_node field.

No, the usb_device needs the .of_node field.

The devices belong to platform bus contains device node.
The devices (usb device) belong to USB bus which are created
dynamically do not contain device node.

-- 

Best Regards,
Peter Chen

On Mon, 18 Jan 2016, Peter Chen wrote:

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Why can't the root_hub reuse dev->dev.of_node?

Indeed, there's no need to add an .of_node field to struct usb_device, 
since the embedded struct device already contains an .of_node field.

No, the usb_device needs the .of_node field.

It already _has_ an .of_node field, in its embedded struct device.

The devices belong to platform bus contains device node.
The devices (usb device) belong to USB bus which are created
dynamically do not contain device node.

I don't know what you mean.  struct usb_device _does_ contain an 
embedded struct device.  It doesn't matter the structures are created 
dynamically, statically, or any other way; this field is part of the 
structure definition.

Suppose udev is a pointer to struct usb_device.  Then udev->dev is a
struct device and udev->dev.of_node is a pointer to struct device_node.  
You don't need to add a new udev->of_node field; just use
udev->dev.of_node instead.

Alan Stern