DFBSD usb_alloc

static usbd_status
usb_block_allocmem(bus_dma_tag_t tag, size_t size, size_t align,
           usb_dma_block_t **dmap)
{
        usb_dma_block_t *p;

    DPRINTFN(5, ("usb_block_allocmem: size=%lu align=%lu\n",
             (u_long)size, (u_long)align));

    crit_enter();
    /* First check the free list. */
    for (p = LIST_FIRST(&usb_blk_freelist); p; p = LIST_NEXT(p, next)) {
        if (p->tag == tag && p->size >= size && p->align >= align) {
            LIST_REMOVE(p, next);
            usb_blk_nfree--;
            crit_exit();
            *dmap = p;
            DPRINTFN(6,("usb_block_allocmem: free list size=%lu\n",
                    (u_long)p->size));
            logmemory(blkalloc2, p, NULL, size, align);
            return (USBD_NORMAL_COMPLETION);
        }
    }
    crit_exit();

    DPRINTFN(6, ("usb_block_allocmem: no free\n"));
    p = kmalloc(sizeof *p, M_USB, M_INTWAIT);
    logmemory(blkalloc, p, NULL, size, align);

    if (bus_dma_tag_create(tag, align, 0,
        BUS_SPACE_MAXADDR_32BIT, BUS_SPACE_MAXADDR, NULL, NULL,
        size, NELEM(p->segs), size, BUS_DMA_ALLOCNOW, &p->tag) == ENOMEM) {
        goto free;
    }

    p->size = size;
    p->align = align;
    if (bus_dmamem_alloc(p->tag, &p->kaddr,
        BUS_DMA_NOWAIT|BUS_DMA_COHERENT, &p->map))
        goto tagfree;

    if (bus_dmamap_load(p->tag, p->map, p->kaddr, p->size,
        usbmem_callback, p, 0))
        goto memfree;

    /* XXX - override the tag, ok since we never free it */
    p->tag = tag;
    *dmap = p;
    return (USBD_NORMAL_COMPLETION);

    /*
     * XXX - do we need to _unload? is the order of _free and _destroy
     * correct?
     */
memfree:
    bus_dmamem_free(p->tag, p->kaddr, p->map);
tagfree:
    bus_dma_tag_destroy(p->tag);
free:
    kfree(p, M_USB);
    return (USBD_NOMEM);
}