drivers/misc/mic/scif/scif_rb.h

   1 /*
   2  * Intel MIC Platform Software Stack (MPSS)
   3  *
   4  * This file is provided under a dual BSD/GPLv2 license.  When using or
   5  * redistributing this file, you may do so under either license.
   6  *
   7  * GPL LICENSE SUMMARY
   8  *
   9  * Copyright(c) 2014 Intel Corporation.
  10  *
  11  * This program is free software; you can redistribute it and/or modify
  12  * it under the terms of version 2 of the GNU General Public License as
  13  * published by the Free Software Foundation.
  14  *
  15  * This program is distributed in the hope that it will be useful, but
  16  * WITHOUT ANY WARRANTY; without even the implied warranty of
  17  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  18  * General Public License for more details.
  19  *
  20  * BSD LICENSE
  21  *
  22  * Copyright(c) 2014 Intel Corporation.
  23  *
  24  * Redistribution and use in source and binary forms, with or without
  25  * modification, are permitted provided that the following conditions
  26  * are met:
  27  *
  28  * * Redistributions of source code must retain the above copyright
  29  *   notice, this list of conditions and the following disclaimer.
  30  * * Redistributions in binary form must reproduce the above copyright
  31  *   notice, this list of conditions and the following disclaimer in
  32  *   the documentation and/or other materials provided with the
  33  *   distribution.
  34  * * Neither the name of Intel Corporation nor the names of its
  35  *   contributors may be used to endorse or promote products derived
  36  *   from this software without specific prior written permission.
  37  *
  38  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  39  * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  40  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
  41  * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
  42  * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  43  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
  44  * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  45  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  46  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  47  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  48  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  49  *
  50  * Intel SCIF driver.
  51  */
  52 #ifndef SCIF_RB_H
  53 #define SCIF_RB_H
  54 /*
  55  * This file describes a general purpose, byte based ring buffer. Writers to the
  56  * ring buffer need to synchronize using a lock. The same is true for readers,
  57  * although in practice, the ring buffer has a single reader. It is lockless
  58  * between producer and consumer so it can handle being used across the PCIe
  59  * bus. The ring buffer ensures that there are no reads across the PCIe bus for
  60  * performance reasons. Two of these are used to form a single bidirectional
  61  * queue-pair across PCIe.
  62  */
  63 /*
  64  * struct scif_rb - SCIF Ring Buffer
  65  *
  66  * @rb_base: The base of the memory used for storing RB messages
  67  * @read_ptr: Pointer to the read offset
  68  * @write_ptr: Pointer to the write offset
  69  * @size: Size of the memory in rb_base
  70  * @current_read_offset: Cached read offset for performance
  71  * @current_write_offset: Cached write offset for performance
  72  */
  73 struct scif_rb {
  74         void *rb_base;
  75         u32 *read_ptr;
  76         u32 *write_ptr;
  77         u32 size;
  78         u32 current_read_offset;
  79         u32 current_write_offset;
  80 };
  81
  82 /* methods used by both */
  83 void scif_rb_init(struct scif_rb *rb, u32 *read_ptr, u32 *write_ptr,
  84                   void *rb_base, u8 size);
  85 /* writer only methods */
  86 /* write a new command, then scif_rb_commit() */
  87 int scif_rb_write(struct scif_rb *rb, void *msg, u32 size);
  88 /* after write(), then scif_rb_commit() */
  89 void scif_rb_commit(struct scif_rb *rb);
  90 /* query space available for writing to a RB. */
  91 u32 scif_rb_space(struct scif_rb *rb);
  92
  93 /* reader only methods */
  94 /* read a new message from the ring buffer of size bytes */
  95 u32 scif_rb_get_next(struct scif_rb *rb, void *msg, u32 size);
  96 /* update the read pointer so that the space can be reused */
  97 void scif_rb_update_read_ptr(struct scif_rb *rb);
  98 /* count the number of bytes that can be read */
  99 u32 scif_rb_count(struct scif_rb *rb, u32 size);
 100 #endif