drivers/infiniband/hw/vmw_pvrdma/pvrdma_ring.h

   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
  53 struct pvrdma_ring {
  54         atomic_t prod_tail;     /* Producer tail. */
  55         atomic_t cons_head;     /* Consumer head. */
  56 };
  57
  58 struct pvrdma_ring_state {
  59         struct pvrdma_ring tx;  /* Tx ring. */
  60         struct pvrdma_ring rx;  /* Rx ring. */
  61 };
  62
  63 static 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
  69 static 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
  78 static 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
  86 static 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
 100 static 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__ */