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__ */ 115