Re: [PATCH 2/5] usb: move struct usb_device->children to struct usb_hub_port->child

[Lan Tianyu <tianyu.lan-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>]

hi alan:
	Great thanks for your such careful review.
On 2012年03月29日 03:13, Alan Stern wrote:
> On Wed, 28 Mar 2012, Lan Tianyu wrote:
>
>> Move child's pointer to the struct usb_hub_port since the child device
>> is directly associated with the port. Provide usb_get_hub_child_device()
>> to get child's pointer.
>
>> --- a/drivers/usb/core/devices.c
>> +++ b/drivers/usb/core/devices.c
>> @@ -590,7 +590,9 @@ static ssize_t usb_device_dump(char __user **buffer, size_t *nbytes,
>>
>>   	/* Now look at all of this device's children. */
>>   	for (chix = 0; chix<  usbdev->maxchild; chix++) {
>> -		struct usb_device *childdev = usbdev->children[chix];
>> +		struct usb_device *childdev;
>> +		if (usb_get_hub_child_device(usbdev, chix + 1,&childdev)<  0)
>> +			continue;
>>
>
> Whitespace issue: The blank line should come before the new executable
> statement, not after it.
>
>> @@ -1475,11 +1477,12 @@ bool usb_device_is_owned(struct usb_device *udev)
>>
>>   static void recursively_mark_NOTATTACHED(struct usb_device *udev)
>>   {
>> +	struct usb_hub	*hub = hdev_to_hub(udev);
>
> I'm not sure this is good.  You are calling hdev_to_hub without knowing
> beforehand that udev really is a hub -- in fact, most of the time udev
> won't be a hub.  The routine wasn't meant to be used that way.  Have
> you checked that hdev_to_hub won't crash when the argument isn't a hub?
> What happens if the active configuration has no interfaces?
About this, I have an idea to add a check of hdev->maxchild. I have
verified that hdev->maxchild only is set in the hub_configure() and
hub_disconnect(). So we can identify whether the udev is a usb hub or
not through hdev->maxchild. Does this make sense?

diff --git a/drivers/usb/core/hub.c b/drivers/usb/core/hub.c
index c70c170..d29a5dc 100644
--- a/drivers/usb/core/hub.c
+++ b/drivers/usb/core/hub.c
@@ -177,7 +177,7 @@ static inline char *portspeed(struct usb_hub *hub, int 
portstatus)
   /* Note that hdev or one of its children must be locked! */
   static struct usb_hub *hdev_to_hub(struct usb_device *hdev)
   {
-       if (!hdev || !hdev->actconfig)
+       if (!hdev || !hdev->actconfig || hdev->maxchild == 0)
                  return NULL;
          return usb_get_intfdata(hdev->actconfig->interface[0]);
   }


>> @@ -4147,3 +4151,15 @@ void usb_queue_reset_device(struct usb_interface *iface)
>>   	schedule_work(&iface->reset_ws);
>>   }
>>   EXPORT_SYMBOL_GPL(usb_queue_reset_device);
>> +
>> +int usb_get_hub_child_device(struct usb_device *hdev, int port1,
>> +	struct usb_device **child)
>> +{
>> +	struct usb_hub *hub = hdev_to_hub(hdev);
>> +
>> +	if (port1>  hdev->maxchild || port1<  1)
>> +		return -EINVAL;
>> +	*child = hub->port_data[port1 - 1].child;
>> +	return 0;
>> +}
>
> This new routine is more complicated that it needs to be.  You don't
> have to return an error code; none of the callers make use of it.
> Just return the child pointer, and return NULL if there's an error.
>
> Alan Stern
>
>

-- 
Best Regards
Tianyu Lan
linux kernel enabling team
--
To unsubscribe from this list: send the line "unsubscribe linux-usb" in
the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html