drivers/misc/ts27010mux/ts27010_ringbuf.h

   1 /*
   2  * simple ring buffer
   3  *
   4  * supports a concurrent reader and writer without locking
   5  */
   6
   7
   8 struct ts27010_ringbuf {
   9         int len;
  10         int head;
  11         int tail;
  12         u8 buf[];
  13 };
  14
  15
  16 static inline struct ts27010_ringbuf *ts27010_ringbuf_alloc(int len)
  17 {
  18         struct ts27010_ringbuf *rbuf;
  19
  20         rbuf = kzalloc(sizeof(*rbuf) + len, GFP_KERNEL);
  21         if (rbuf == NULL)
  22                 return NULL;
  23
  24         rbuf->len = len;
  25         rbuf->head = 0;
  26         rbuf->tail = 0;
  27
  28         return rbuf;
  29 }
  30
  31 static inline void ts27010_ringbuf_free(struct ts27010_ringbuf *rbuf)
  32 {
  33         kfree(rbuf);
  34 }
  35
  36 static inline int ts27010_ringbuf_level(struct ts27010_ringbuf *rbuf)
  37 {
  38         int level = rbuf->head - rbuf->tail;
  39
  40         if (level < 0)
  41                 level = rbuf->len + level;
  42
  43         return level;
  44 }
  45
  46 static inline int ts27010_ringbuf_room(struct ts27010_ringbuf *rbuf)
  47 {
  48         return rbuf->len - ts27010_ringbuf_level(rbuf) - 1;
  49 }
  50
  51 static inline u8 ts27010_ringbuf_peek(struct ts27010_ringbuf *rbuf, int i)
  52 {
  53         return rbuf->buf[(rbuf->tail + i) % rbuf->len];
  54 }
  55
  56 static inline int ts27010_ringbuf_consume(struct ts27010_ringbuf *rbuf,
  57                                           int count)
  58 {
  59         count = min(count, ts27010_ringbuf_level(rbuf));
  60
  61         rbuf->tail = (rbuf->tail + count) % rbuf->len;
  62
  63         return count;
  64 }
  65
  66 static inline int ts27010_ringbuf_push(struct ts27010_ringbuf *rbuf, u8 datum)
  67 {
  68         if (ts27010_ringbuf_room(rbuf) == 0)
  69                 return 0;
  70
  71         rbuf->buf[rbuf->head] = datum;
  72         rbuf->head = (rbuf->head + 1) % rbuf->len;
  73
  74         return 1;
  75 }
  76
  77 static inline int ts27010_ringbuf_write(struct ts27010_ringbuf *rbuf,
  78                                         const u8 *data, int len)
  79 {
  80         int count = 0;
  81         int i;
  82
  83         for (i = 0; i < len; i++)
  84                 count += ts27010_ringbuf_push(rbuf, data[i]);
  85
  86         return count;
  87 }
  88
  89