[mnyman-xhci:fix_ring_expansion 2/2] drivers/usb/host/xhci-ring.c:300:11: warning: variable 'free' is uninitialized when used here

[mnyman-xhci:fix_ring_expansion 2/2] drivers/usb/host/xhci-ring.c:300:11: warning: variable 'free' is uninitialized when used here

[kernel test robot]

tree:   https://git.kernel.org/pub/scm/linux/kernel/git/mnyman/xhci.git fix_ring_expansion
head:   5d43e1a13408572e6bf8f7d91c9b26825f0287a9
commit: 5d43e1a13408572e6bf8f7d91c9b26825f0287a9 [2/2] xhci: Stop unnecessary and incorrect tracking of free trbs in a ring
config: x86_64-randconfig-a003-20230424 (https://download.01.org/0day-ci/archive/20230426/202304261531.wNaJdrf8-lkp@intel.com/config)
compiler: clang version 14.0.6 (https://github.com/llvm/llvm-project f28c006a5895fc0e329fe15fead81e37457cb1d1)
reproduce (this is a W=1 build):
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # https://git.kernel.org/pub/scm/linux/kernel/git/mnyman/xhci.git/commit/?id=5d43e1a13408572e6bf8f7d91c9b26825f0287a9
        git remote add mnyman-xhci https://git.kernel.org/pub/scm/linux/kernel/git/mnyman/xhci.git
        git fetch --no-tags mnyman-xhci fix_ring_expansion
        git checkout 5d43e1a13408572e6bf8f7d91c9b26825f0287a9
        # save the config file
        mkdir build_dir && cp config build_dir/.config
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross W=1 O=build_dir ARCH=x86_64 olddefconfig
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross W=1 O=build_dir ARCH=x86_64 SHELL=/bin/bash

If you fix the issue, kindly add following tag where applicable
| Reported-by: kernel test robot <lkp@intel.com>
| Link: https://lore.kernel.org/oe-kbuild-all/202304261531.wNaJdrf8-lkp@intel.com/

All warnings (new ones prefixed by >>):

>> drivers/usb/host/xhci-ring.c:300:11: warning: variable 'free' is uninitialized when used here [-Wuninitialized]
                           return free + (ring->dequeue - enq);
                                  ^~~~
   drivers/usb/host/xhci-ring.c:285:19: note: initialize the variable 'free' to silence this warning
           unsigned int free;
                            ^
                             = 0
>> drivers/usb/host/xhci-ring.c:305:11: warning: variable 'i' is uninitialized when used here [-Wuninitialized]
           } while (i++ <= ring->num_segs);
                    ^
   drivers/usb/host/xhci-ring.c:286:7: note: initialize the variable 'i' to silence this warning
           int i;
                ^
                 = 0
   2 warnings generated.


vim +/free +300 drivers/usb/host/xhci-ring.c

   273	
   274	/*
   275	 * Return number of free normal TRBs from enqueue to dequeue pointer on ring.
   276	 * Not counting an assumed link TRB at end of each TRBS_PER_SEGMENT sized segment.
   277	 * Only for transfer and command rings where driver is the producer, not for
   278	 * event rings.
   279	 */
   280	static unsigned int xhci_num_trbs_free(struct xhci_hcd *xhci, struct xhci_ring *ring)
   281	{
   282		struct xhci_segment *enq_seg = ring->enq_seg;
   283		union xhci_trb *enq = ring->enqueue;
   284		union xhci_trb *last_on_seg;
   285		unsigned int free;
   286		int i;
   287	
   288		/* Ring might be empty even if enq != deq if enq is left on a link trb */
   289		if (trb_is_link(enq)) {
   290			enq_seg = enq_seg->next;
   291			enq = enq_seg->trbs;
   292		}
   293	
   294		/* Empty ring, common case, don't walk the segments */
   295		if (enq == ring->dequeue)
   296			return ring->num_segs * (TRBS_PER_SEGMENT - 1);
   297	
   298		do {
   299			if (ring->deq_seg == enq_seg && ring->dequeue >= enq)
 > 300				return free + (ring->dequeue - enq);
   301			last_on_seg = &enq_seg->trbs[TRBS_PER_SEGMENT - 1];
   302			free += last_on_seg - enq;
   303			enq_seg = enq_seg->next;
   304			enq = enq_seg->trbs;
 > 305		} while (i++ <= ring->num_segs);
   306	
   307		return free;
   308	}
   309	

-- 
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests