LXR linux/drivers/infiniband/hw/vmw_pvrdma/pvrdma

   1/*
   2 * Copyright (c) 2012-2016 VMware, Inc.  All rights reserved.
   3 *
   4 * This program is free software; you can redistribute it and/or
   5 * modify it under the terms of EITHER the GNU General Public License
   6 * version 2 as published by the Free Software Foundation or the BSD
   7 * 2-Clause License. This program is distributed in the hope that it
   8 * will be useful, but WITHOUT ANY WARRANTY; WITHOUT EVEN THE IMPLIED
   9 * WARRANTY OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
  10 * See the GNU General Public License version 2 for more details at
  11 * http://www.gnu.org/licenses/old-licenses/gpl-2.0.en.html.
  12 *
  13 * You should have received a copy of the GNU General Public License
  14 * along with this program available in the file COPYING in the main
  15 * directory of this source tree.
  16 *
  17 * The BSD 2-Clause License
  18 *
  19 *     Redistribution and use in source and binary forms, with or
  20 *     without modification, are permitted provided that the following
  21 *     conditions are met:
  22 *
  23 *      - Redistributions of source code must retain the above
  24 *        copyright notice, this list of conditions and the following
  25 *        disclaimer.
  26 *
  27 *      - Redistributions in binary form must reproduce the above
  28 *        copyright notice, this list of conditions and the following
  29 *        disclaimer in the documentation and/or other materials
  30 *        provided with the distribution.
  31 *
  32 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  33 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  34 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
  35 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
  36 * COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
  37 * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
  38 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
  39 * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  40 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
  41 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
  42 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
  43 * OF THE POSSIBILITY OF SUCH DAMAGE.
  44 */
  45
  46#ifndef __PVRDMA_RING_H__
  47#define __PVRDMA_RING_H__
  48
  49#include <linux/types.h>
  50
  51#define PVRDMA_INVALID_IDX      -1      /* Invalid index. */
  52
  53struct pvrdma_ring {
  54        atomic_t prod_tail;     /* Producer tail. */
  55        atomic_t cons_head;     /* Consumer head. */
  56};
  57
  58struct pvrdma_ring_state {
  59        struct pvrdma_ring tx;  /* Tx ring. */
  60        struct pvrdma_ring rx;  /* Rx ring. */
  61};
  62
  63static inline int pvrdma_idx_valid(__u32 idx, __u32 max_elems)
  64{
  65        /* Generates fewer instructions than a less-than. */
  66        return (idx & ~((max_elems << 1) - 1)) == 0;
  67}
  68
  69static inline __s32 pvrdma_idx(atomic_t *var, __u32 max_elems)
  70{
  71        const unsigned int idx = atomic_read(var);
  72
  73        if (pvrdma_idx_valid(idx, max_elems))
  74                return idx & (max_elems - 1);
  75        return PVRDMA_INVALID_IDX;
  76}
  77
  78static inline void pvrdma_idx_ring_inc(atomic_t *var, __u32 max_elems)
  79{
  80        __u32 idx = atomic_read(var) + 1;       /* Increment. */
  81
  82        idx &= (max_elems << 1) - 1;            /* Modulo size, flip gen. */
  83        atomic_set(var, idx);
  84}
  85
  86static inline __s32 pvrdma_idx_ring_has_space(const struct pvrdma_ring *r,
  87                                              __u32 max_elems, __u32 *out_tail)
  88{
  89        const __u32 tail = atomic_read(&r->prod_tail);
  90        const __u32 head = atomic_read(&r->cons_head);
  91
  92        if (pvrdma_idx_valid(tail, max_elems) &&
  93            pvrdma_idx_valid(head, max_elems)) {
  94                *out_tail = tail & (max_elems - 1);
  95                return tail != (head ^ max_elems);
  96        }
  97        return PVRDMA_INVALID_IDX;
  98}
  99
 100static inline __s32 pvrdma_idx_ring_has_data(const struct pvrdma_ring *r,
 101                                             __u32 max_elems, __u32 *out_head)
 102{
 103        const __u32 tail = atomic_read(&r->prod_tail);
 104        const __u32 head = atomic_read(&r->cons_head);
 105
 106        if (pvrdma_idx_valid(tail, max_elems) &&
 107            pvrdma_idx_valid(head, max_elems)) {
 108                *out_head = head & (max_elems - 1);
 109                return tail != head;
 110        }
 111        return PVRDMA_INVALID_IDX;
 112}
 113
 114#endif /* __PVRDMA_RING_H__ */
 115