3 * Copyright (C) 2010 - 2013 UNISYS CORPORATION
6 * This program is free software; you can redistribute it and/or modify
7 * it under the terms of the GNU General Public License as published by
8 * the Free Software Foundation; either version 2 of the License, or (at
9 * your option) any later version.
11 * This program is distributed in the hope that it will be useful, but
12 * WITHOUT ANY WARRANTY; without even the implied warranty of
13 * MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE, GOOD TITLE or
14 * NON INFRINGEMENT. See the GNU General Public License for more
19 * Simple character queue implementation for Linux kernel mode.
22 #include "charqueue.h"
24 #define MYDRVNAME "charqueue"
26 #define IS_EMPTY(charqueue) (charqueue->head == charqueue->tail)
31 spinlock_t lock; /* read/write lock for this structure */
36 struct charqueue *visor_charqueue_create(ulong nslots)
38 int alloc_size = sizeof(struct charqueue) + nslots + 1;
41 cq = kmalloc(alloc_size, GFP_KERNEL|__GFP_NORETRY);
44 cq->alloc_size = alloc_size;
48 spin_lock_init(&cq->lock);
51 EXPORT_SYMBOL_GPL(visor_charqueue_create);
53 void visor_charqueue_enqueue(struct charqueue *charqueue, unsigned char c)
55 int alloc_slots = charqueue->nslots+1; /* 1 slot is always empty */
57 spin_lock(&charqueue->lock);
58 charqueue->head = (charqueue->head+1) % alloc_slots;
59 if (charqueue->head == charqueue->tail)
60 /* overflow; overwrite the oldest entry */
61 charqueue->tail = (charqueue->tail+1) % alloc_slots;
62 charqueue->buf[charqueue->head] = c;
63 spin_unlock(&charqueue->lock);
65 EXPORT_SYMBOL_GPL(visor_charqueue_enqueue);
67 BOOL visor_charqueue_is_empty(struct charqueue *charqueue)
71 spin_lock(&charqueue->lock);
72 b = IS_EMPTY(charqueue);
73 spin_unlock(&charqueue->lock);
76 EXPORT_SYMBOL_GPL(visor_charqueue_is_empty);
78 static int charqueue_dequeue_1(struct charqueue *charqueue)
80 int alloc_slots = charqueue->nslots + 1; /* 1 slot is always empty */
82 if (IS_EMPTY(charqueue))
84 charqueue->tail = (charqueue->tail+1) % alloc_slots;
85 return charqueue->buf[charqueue->tail];
88 int charqueue_dequeue(struct charqueue *charqueue)
92 spin_lock(&charqueue->lock);
93 rc = charqueue_dequeue_1(charqueue);
94 spin_unlock(&charqueue->lock);
98 int visor_charqueue_dequeue_n(struct charqueue *charqueue, unsigned char *buf,
101 int rc, counter = 0, c;
103 spin_lock(&charqueue->lock);
106 break; /* no more buffer space */
107 c = charqueue_dequeue_1(charqueue);
109 break; /* no more input */
110 *buf = (unsigned char)(c);
116 spin_unlock(&charqueue->lock);
119 EXPORT_SYMBOL_GPL(visor_charqueue_dequeue_n);
121 void visor_charqueue_destroy(struct charqueue *charqueue)
123 if (charqueue == NULL)
127 EXPORT_SYMBOL_GPL(visor_charqueue_destroy);