arch/arm/common/fiq_debugger_ringbuf.h

   1 /*
   2  * arch/arm/common/fiq_debugger_ringbuf.c
   3  *
   4  * simple lockless ringbuffer
   5  *
   6  * Copyright (C) 2010 Google, Inc.
   7  *
   8  * This software is licensed under the terms of the GNU General Public
   9  * License version 2, as published by the Free Software Foundation, and
  10  * may be copied, distributed, and modified under those terms.
  11  *
  12  * This program is distributed in the hope that it will be useful,
  13  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15  * GNU General Public License for more details.
  16  */
  17
  18 #include <linux/kernel.h>
  19 #include <linux/slab.h>
  20
  21 struct fiq_debugger_ringbuf {
  22         int len;
  23         int head;
  24         int tail;
  25         u8 buf[];
  26 };
  27
  28
  29 static inline struct fiq_debugger_ringbuf *fiq_debugger_ringbuf_alloc(int len)
  30 {
  31         struct fiq_debugger_ringbuf *rbuf;
  32
  33         rbuf = kzalloc(sizeof(*rbuf) + len, GFP_KERNEL);
  34         if (rbuf == NULL)
  35                 return NULL;
  36
  37         rbuf->len = len;
  38         rbuf->head = 0;
  39         rbuf->tail = 0;
  40         smp_mb();
  41
  42         return rbuf;
  43 }
  44
  45 static inline void fiq_debugger_ringbuf_free(struct fiq_debugger_ringbuf *rbuf)
  46 {
  47         kfree(rbuf);
  48 }
  49
  50 static inline int fiq_debugger_ringbuf_level(struct fiq_debugger_ringbuf *rbuf)
  51 {
  52         int level = rbuf->head - rbuf->tail;
  53
  54         if (level < 0)
  55                 level = rbuf->len + level;
  56
  57         return level;
  58 }
  59
  60 static inline int fiq_debugger_ringbuf_room(struct fiq_debugger_ringbuf *rbuf)
  61 {
  62         return rbuf->len - fiq_debugger_ringbuf_level(rbuf) - 1;
  63 }
  64
  65 static inline u8
  66 fiq_debugger_ringbuf_peek(struct fiq_debugger_ringbuf *rbuf, int i)
  67 {
  68         return rbuf->buf[(rbuf->tail + i) % rbuf->len];
  69 }
  70
  71 static inline int
  72 fiq_debugger_ringbuf_consume(struct fiq_debugger_ringbuf *rbuf, int count)
  73 {
  74         count = min(count, fiq_debugger_ringbuf_level(rbuf));
  75
  76         rbuf->tail = (rbuf->tail + count) % rbuf->len;
  77         smp_mb();
  78
  79         return count;
  80 }
  81
  82 static inline int
  83 fiq_debugger_ringbuf_push(struct fiq_debugger_ringbuf *rbuf, u8 datum)
  84 {
  85         if (fiq_debugger_ringbuf_room(rbuf) == 0)
  86                 return 0;
  87
  88         rbuf->buf[rbuf->head] = datum;
  89         smp_mb();
  90         rbuf->head = (rbuf->head + 1) % rbuf->len;
  91         smp_mb();
  92
  93         return 1;
  94 }