+ pb->buf_size = size;
+ pb->buf_get = pb->buf_put = pb->buf_buf;
+
+ return pb;
+
+}
+
+
+/*
+ * pl2303_buf_free
+ *
+ * Free the buffer and all associated memory.
+ */
+
+static void pl2303_buf_free(struct pl2303_buf *pb)
+{
+ if (pb != NULL) {
+ if (pb->buf_buf != NULL)
+ kfree(pb->buf_buf);
+ kfree(pb);
+ }
+}
+
+
+/*
+ * pl2303_buf_clear
+ *
+ * Clear out all data in the circular buffer.
+ */
+
+static void pl2303_buf_clear(struct pl2303_buf *pb)
+{
+ if (pb != NULL)
+ pb->buf_get = pb->buf_put;
+ /* equivalent to a get of all data available */
+}
+
+
+/*
+ * pl2303_buf_data_avail
+ *
+ * Return the number of bytes of data available in the circular
+ * buffer.
+ */
+
+static unsigned int pl2303_buf_data_avail(struct pl2303_buf *pb)
+{
+ if (pb != NULL)
+ return ((pb->buf_size + pb->buf_put - pb->buf_get) % pb->buf_size);
+ else
+ return 0;
+}
+
+
+/*
+ * pl2303_buf_space_avail
+ *
+ * Return the number of bytes of space available in the circular
+ * buffer.
+ */
+
+static unsigned int pl2303_buf_space_avail(struct pl2303_buf *pb)
+{
+ if (pb != NULL)
+ return ((pb->buf_size + pb->buf_get - pb->buf_put - 1) % pb->buf_size);
+ else
+ return 0;
+}
+
+
+/*
+ * pl2303_buf_put
+ *
+ * Copy data data from a user buffer and put it into the circular buffer.
+ * Restrict to the amount of space available.
+ *
+ * Return the number of bytes copied.
+ */
+
+static unsigned int pl2303_buf_put(struct pl2303_buf *pb, const char *buf,
+ unsigned int count)
+{
+
+ unsigned int len;
+
+
+ if (pb == NULL)
+ return 0;
+
+ len = pl2303_buf_space_avail(pb);
+ if (count > len)
+ count = len;
+
+ if (count == 0)
+ return 0;
+
+ len = pb->buf_buf + pb->buf_size - pb->buf_put;
+ if (count > len) {
+ memcpy(pb->buf_put, buf, len);
+ memcpy(pb->buf_buf, buf+len, count - len);
+ pb->buf_put = pb->buf_buf + count - len;
+ } else {
+ memcpy(pb->buf_put, buf, count);
+ if (count < len)
+ pb->buf_put += count;
+ else /* count == len */
+ pb->buf_put = pb->buf_buf;
+ }
+
+ return count;
+