115 lines
3.9 KiB
C
115 lines
3.9 KiB
C
/*
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* Copyright (c) 2012-2016 VMware, Inc. All rights reserved.
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of EITHER the GNU General Public License
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* version 2 as published by the Free Software Foundation or the BSD
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* 2-Clause License. This program is distributed in the hope that it
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* will be useful, but WITHOUT ANY WARRANTY; WITHOUT EVEN THE IMPLIED
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* WARRANTY OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
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* See the GNU General Public License version 2 for more details at
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* http://www.gnu.org/licenses/old-licenses/gpl-2.0.en.html.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program available in the file COPYING in the main
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* directory of this source tree.
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*
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* The BSD 2-Clause License
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*
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* Redistribution and use in source and binary forms, with or
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* without modification, are permitted provided that the following
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* conditions are met:
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*
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* - Redistributions of source code must retain the above
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* copyright notice, this list of conditions and the following
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* disclaimer.
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*
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* - Redistributions in binary form must reproduce the above
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* copyright notice, this list of conditions and the following
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* disclaimer in the documentation and/or other materials
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* provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
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* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
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* COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
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* INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
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* (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
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* SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
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* STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
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* OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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#ifndef __PVRDMA_RING_H__
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#define __PVRDMA_RING_H__
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#include <linux/types.h>
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#define PVRDMA_INVALID_IDX -1 /* Invalid index. */
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struct pvrdma_ring {
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atomic_t prod_tail; /* Producer tail. */
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atomic_t cons_head; /* Consumer head. */
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};
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struct pvrdma_ring_state {
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struct pvrdma_ring tx; /* Tx ring. */
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struct pvrdma_ring rx; /* Rx ring. */
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};
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static inline int pvrdma_idx_valid(__u32 idx, __u32 max_elems)
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{
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/* Generates fewer instructions than a less-than. */
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return (idx & ~((max_elems << 1) - 1)) == 0;
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}
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static inline __s32 pvrdma_idx(atomic_t *var, __u32 max_elems)
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{
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const unsigned int idx = atomic_read(var);
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if (pvrdma_idx_valid(idx, max_elems))
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return idx & (max_elems - 1);
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return PVRDMA_INVALID_IDX;
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}
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static inline void pvrdma_idx_ring_inc(atomic_t *var, __u32 max_elems)
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{
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__u32 idx = atomic_read(var) + 1; /* Increment. */
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idx &= (max_elems << 1) - 1; /* Modulo size, flip gen. */
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atomic_set(var, idx);
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}
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static inline __s32 pvrdma_idx_ring_has_space(const struct pvrdma_ring *r,
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__u32 max_elems, __u32 *out_tail)
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{
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const __u32 tail = atomic_read(&r->prod_tail);
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const __u32 head = atomic_read(&r->cons_head);
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if (pvrdma_idx_valid(tail, max_elems) &&
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pvrdma_idx_valid(head, max_elems)) {
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*out_tail = tail & (max_elems - 1);
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return tail != (head ^ max_elems);
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}
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return PVRDMA_INVALID_IDX;
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}
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static inline __s32 pvrdma_idx_ring_has_data(const struct pvrdma_ring *r,
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__u32 max_elems, __u32 *out_head)
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{
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const __u32 tail = atomic_read(&r->prod_tail);
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const __u32 head = atomic_read(&r->cons_head);
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if (pvrdma_idx_valid(tail, max_elems) &&
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pvrdma_idx_valid(head, max_elems)) {
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*out_head = head & (max_elems - 1);
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return tail != head;
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}
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return PVRDMA_INVALID_IDX;
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}
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#endif /* __PVRDMA_RING_H__ */
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