seg = kzalloc(sizeof *seg, flags);
        if (!seg)
-               return 0;
+               return NULL;
        xhci_dbg(xhci, "Allocating priv segment structure at %p\n", seg);
 
        seg->trbs = dma_pool_alloc(xhci->segment_pool, flags, &dma);
        if (!seg->trbs) {
                kfree(seg);
-               return 0;
+               return NULL;
        }
        xhci_dbg(xhci, "// Allocating segment at %p (virtual) 0x%llx (DMA)\n",
                        seg->trbs, (unsigned long long)dma);
        ring = kzalloc(sizeof *(ring), flags);
        xhci_dbg(xhci, "Allocating ring at %p\n", ring);
        if (!ring)
-               return 0;
+               return NULL;
 
        INIT_LIST_HEAD(&ring->td_list);
        if (num_segs == 0)
 
 fail:
        xhci_ring_free(xhci, ring);
-       return 0;
+       return NULL;
 }
 
 void xhci_free_or_cache_endpoint_ring(struct xhci_hcd *xhci,
 
 #define CTX_SIZE(_hcc) (HCC_64BYTE_CONTEXT(_hcc) ? 64 : 32)
 
-struct xhci_container_ctx *xhci_alloc_container_ctx(struct xhci_hcd *xhci,
+static struct xhci_container_ctx *xhci_alloc_container_ctx(struct xhci_hcd *xhci,
                                                    int type, gfp_t flags)
 {
        struct xhci_container_ctx *ctx = kzalloc(sizeof(*ctx), flags);
        return ctx;
 }
 
-void xhci_free_container_ctx(struct xhci_hcd *xhci,
+static void xhci_free_container_ctx(struct xhci_hcd *xhci,
                             struct xhci_container_ctx *ctx)
 {
        if (!ctx)
                xhci_free_container_ctx(xhci, dev->out_ctx);
 
        kfree(xhci->devs[slot_id]);
-       xhci->devs[slot_id] = 0;
+       xhci->devs[slot_id] = NULL;
 }
 
 int xhci_alloc_virt_device(struct xhci_hcd *xhci, int slot_id,
         */
        init_completion(&xhci->addr_dev);
        for (i = 0; i < MAX_HC_SLOTS; ++i)
-               xhci->devs[i] = 0;
+               xhci->devs[i] = NULL;
 
        if (scratchpad_alloc(xhci, flags))
                goto fail;
 
                cur_seg = cur_seg->next;
                if (cur_seg == start_seg)
                        /* Looped over the entire list.  Oops! */
-                       return 0;
+                       return NULL;
        }
        return cur_seg;
 }
        struct xhci_ring *ep_ring;
        struct xhci_virt_ep *ep;
        struct list_head *entry;
-       struct xhci_td *cur_td = 0;
+       struct xhci_td *cur_td = NULL;
        struct xhci_td *last_unlinked_td;
 
        struct xhci_dequeue_state deq_state;
 
        do {
                if (start_dma == 0)
-                       return 0;
+                       return NULL;
                /* We may get an event for a Link TRB in the middle of a TD */
                end_seg_dma = xhci_trb_virt_to_dma(cur_seg,
                                &cur_seg->trbs[TRBS_PER_SEGMENT - 1]);
                                                 suspect_dma <= end_trb_dma))
                                        return cur_seg;
                        }
-                       return 0;
+                       return NULL;
                } else {
                        /* Might still be somewhere in this segment */
                        if (suspect_dma >= start_dma && suspect_dma <= end_seg_dma)
                start_dma = xhci_trb_virt_to_dma(cur_seg, &cur_seg->trbs[0]);
        } while (cur_seg != start_seg);
 
-       return 0;
+       return NULL;
 }
 
 static void xhci_cleanup_halted_endpoint(struct xhci_hcd *xhci,
        struct xhci_ring *ep_ring;
        unsigned int slot_id;
        int ep_index;
-       struct xhci_td *td = 0;
+       struct xhci_td *td = NULL;
        dma_addr_t event_dma;
        struct xhci_segment *event_seg;
        union xhci_trb *event_trb;
-       struct urb *urb = 0;
+       struct urb *urb = NULL;
        int status = -EINPROGRESS;
        struct xhci_ep_ctx *ep_ctx;
        u32 trb_comp_code;