Re: [balbi-usb:merge-result-for-greg 66/99] drivers/usb/core/hub.c:2654 usb_get_hub_port_power_state() error: doing dma on the stack ((null))

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On 2012/9/12 21:11, Alan Stern wrote:
On Wed, 12 Sep 2012, Fengguang Wu wrote:

Hi Felipe,

FYI, there are new smatch warnings show up in

tree:   git://git.kernel.org/pub/scm/linux/kernel/git/balbi/usb.git merge-result-for-greg
head:   23953bde3e4d6aa8780dc054f6ad9882ac63f4f4
commit: e918fa161f510136fce45a524e934fe20e62c8b1 [66/99] Merge tag 'gadget-for-v3.7' into merge-result-for-greg

drivers/usb/core/hub.c:2654 usb_get_hub_port_power_state() error: doing dma on the stack ((null))
drivers/usb/core/hub.c:4733 store_port_power_control() info: why not propagate 'ret' from set_port_feature() instead of -5?
drivers/usb/core/hub.c:4744 store_port_power_control() info: why not propagate 'ret' from clear_port_feature() instead of -5?

vim +2654 drivers/usb/core/hub.c
   2644		return ret;
   2645	}
   2646	
   2647	static int usb_get_hub_port_power_state(struct usb_device *hdev, int port1)
   2648	{
   2649		struct usb_hub *hub = hdev_to_hub(hdev);
   2650		struct usb_port_status data;
   2651		u16 portstatus;
   2652		int ret;
   2653	
2654		ret = get_port_status(hub->hdev, port1, &data);
   2655		if (ret < 4) {
   2656			dev_err(hub->intfdev,
   2657				"%s failed (err = %d)\n", __func__, ret);
   2658			if (ret >= 0)
   2659				ret = -EIO;
   2660			return ret;
   2661		} else
   2662			portstatus = le16_to_cpu(data.wPortStatus);
   2663		return port_is_power_on(hub, portstatus);
   2664	}

This is a real problem.  It looks like it really is necessary to call
hub_port_status() here, not get_port_status().  Would you like to fix
this?

Yeah. I'd like to fix it.
The reason for changing the return codes from clear_port_feature() and
set_port_feature() is simple.  The values they return are meant for
internal use within the kernel, whereas the return code from
store_port_power_control() will be passed back to userspace.

Alan Stern



--
Best Regards
Tianyu Lan
linux kernel enabling team
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