[bug report] ACPI: Add new IORT functions to support MSI domain handling

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

Hello Tomasz Nowicki,

The patch 4bf2efd26d76: "ACPI: Add new IORT functions to support MSI
domain handling" from Sep 12, 2016, leads to the following static
checker warning:

	drivers/acpi/arm64/iort.c:628 iort_dev_find_its_id()
	warn: array off by one? 'its->identifiers[idx]'

drivers/acpi/arm64/iort.c
   589  /**
   590   * iort_dev_find_its_id() - Find the ITS identifier for a device
   591   * @dev: The device.
   592   * @req_id: Device's requester ID
   593   * @idx: Index of the ITS identifier list.
   594   * @its_id: ITS identifier.
   595   *
   596   * Returns: 0 on success, appropriate error value otherwise
   597   */
   598  static int iort_dev_find_its_id(struct device *dev, u32 req_id,
   599                                  unsigned int idx, int *its_id)
   600  {
   601          struct acpi_iort_its_group *its;
   602          struct acpi_iort_node *node;
   603  
   604          node = iort_find_dev_node(dev);
   605          if (!node)
   606                  return -ENXIO;
   607  
   608          node = iort_node_map_id(node, req_id, NULL, IORT_MSI_TYPE);
   609          if (!node)
   610                  return -ENXIO;
   611  
   612          /* Move to ITS specific data */
   613          its = (struct acpi_iort_its_group *)node->node_data;
   614          if (idx > its->its_count) {
                    ^^^^^^^^^^^^^^^^^^^^
I wasn't able to find any information about how its->its_count is set
but it looks to me that is off by one.

   615                  dev_err(dev, "requested ITS ID index [%d] is greater than available [%d]\n",
   616                          idx, its->its_count);
   617                  return -ENXIO;
   618          }
   619  
   620          *its_id = its->identifiers[idx];
   621          return 0;
   622  }

regards,
dan carpenter