[bug report] ACPI: EC: Avoid passing redundant argument to functions

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

Hello Rafael J. Wysocki,

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

The patch a2b691772acd: "ACPI: EC: Avoid passing redundant argument 
to functions" from Feb 27, 2020, leads to the following Smatch 
complaint:

    drivers/acpi/ec.c:1624 acpi_ec_add()
    error: we previously assumed 'ec' could be null (see line 1595)

drivers/acpi/ec.c
  1588  
  1589          strcpy(acpi_device_name(device), ACPI_EC_DEVICE_NAME);
  1590          strcpy(acpi_device_class(device), ACPI_EC_CLASS);
  1591  
  1592          if ((boot_ec && boot_ec->handle == device->handle) ||
                     ^^^^^^^
Assume "boot_ec" is NULL.

  1593              !strcmp(acpi_device_hid(device), ACPI_ECDT_HID)) {

And the strings math.

  1594			/* Fast path: this device corresponds to the boot EC. */
  1595			ec = boot_ec;
                        ^^^^^^^^^^^^
so "ec" is NULL.

  1596		} else {
  1597			acpi_status status;
  1598	
  1599			ec = acpi_ec_alloc();
  1600			if (!ec)
  1601				return -ENOMEM;
  1602	
  1603			status = ec_parse_device(device->handle, 0, ec, NULL);
  1604			if (status != AE_CTRL_TERMINATE) {
  1605				ret = -EINVAL;
  1606				goto err;
  1607			}
  1608	
  1609			if (boot_ec && ec->command_addr == boot_ec->command_addr &&
  1610			    ec->data_addr == boot_ec->data_addr) {
  1611				/*
  1612				 * Trust PNP0C09 namespace location rather than
  1613				 * ECDT ID. But trust ECDT GPE rather than _GPE
  1614				 * because of ASUS quirks, so do not change
  1615				 * boot_ec->gpe to ec->gpe.
  1616				 */
  1617				boot_ec->handle = ec->handle;
  1618				acpi_handle_debug(ec->handle, "duplicated.\n");
  1619				acpi_ec_free(ec);
  1620				ec = boot_ec;
  1621			}
  1622		}
  1623	
  1624		ret = acpi_ec_setup(ec, device);
                                    ^^
NULL dereference inside the function.

  1625		if (ret)
  1626			goto err;

regards,
dan carpenter