cxgb4: add common api support for configuring filters

Hello Rahul Lakkireddy,

The patch 578b46b9383c: "cxgb4: add common api support for configuring filters" from Sep 20, 2016, leads to the following static checker warning:

	drivers/net/ethernet/chelsio/cxgb4/cxgb4_filter.c:1341 __cxgb4_set_filter()
	warn: we tested 'f->valid' before and it was 'false'

drivers/net/ethernet/chelsio/cxgb4/cxgb4_filter.c
1313
1314 /* Check to make sure that provided filter index is not
1315 * already in use by someone else
1316 */
1317 f = &adapter->tids.ftid_tab[filter_id];
1318 if (f->valid)

                    ^^^^^^^^

Checked.

1319 return -EBUSY;
1320
1321 fidx = filter_id + adapter->tids.ftid_base;
1322 ret = cxgb4_set_ftid(&adapter->tids, filter_id,
1323 fs->type ? PF_INET6 : PF_INET,
1324 chip_ver);
1325 if (ret)
1326 return ret;
1327

  1328          /* Check t  make sure the filter requested is writable ... */
  1329          ret = writable_filter(f);
  1330          if (ret) {
  1331                  /* Clear the bits we have set above */
  1332                  cxgb4_clear_ftid(&adapter->tids, filter_id,
  1333                                   fs->type ? PF_INET6 : PF_INET,
  1334                                   chip_ver);
  1335                  return ret;
  1336          }
  1337  
  1338          /* Clear out any old resources being used by the filter before
  1339           * we start constructing the new filter.
  1340           */
  1341          if (f->valid)
                    ^^^^^^^^

I don't think this can be true.

  1342                  clear_filter(adapter, f);
  1343  

regards,
dan carpenter