re: xen/acpi: ACPI memory hotplug

[Dan Carpenter <dan.carpenter@oracle.com>]

Hello Liu Jinsong,

This is a semi-automatic email about new static checker warnings.

The patch 259f201cb7ea: "xen/acpi: ACPI memory hotplug" from Jan 24, 
2013, leads to the following Smatch complaint:

drivers/xen/xen-acpi-memhotplug.c:198 acpi_memory_get_device()
	 error: we previously assumed 'device' could be null (see line 171)

drivers/xen/xen-acpi-memhotplug.c
   170	
   171		if (!acpi_bus_get_device(handle, &device) && device)
                                                             ^^^^^^
New check.

Btw, checking device is unnecessary.

		if (acpi_bus_get_device(handle, &device) == 0)
			goto end;

A successful "Get Device" means that "device" is non-NULL; that's built
into the name.  Anyway, if acpi_bus_get_device() fails either something
else will fail or we will Oops in the call to acpi_driver_data().

   172			goto end;
   173	
   174		status = acpi_get_parent(handle, &phandle);
   175		if (ACPI_FAILURE(status)) {
   176			pr_warn(PREFIX "Cannot find acpi parent\n");
   177			return -EINVAL;
   178		}
   179	
   180		/* Get the parent device */
   181		result = acpi_bus_get_device(phandle, &pdevice);
   182		if (result) {
   183			pr_warn(PREFIX "Cannot get acpi bus device\n");
   184			return -EINVAL;
   185		}
   186	
   187		/*
   188		 * Now add the notified device.  This creates the acpi_device
   189		 * and invokes .add function
   190		 */
   191		result = acpi_bus_scan(handle);
   192		if (result) {
   193			pr_warn(PREFIX "Cannot add acpi bus\n");
   194			return -EINVAL;
   195		}
   196	
   197	end:
   198		*mem_device = acpi_driver_data(device);
                                               ^^^^^^
Dereference.

   199		if (!(*mem_device)) {
   200			pr_err(PREFIX "Driver data not found\n");

regards,
dan carpenter