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