nuttx/1wire: Adds 1wire master interface

This implements a new master interface to handle the 1-wire transition in an
atomic sense.

Signed-off-by: Marco Krahl <ocram.lhark@gmail.com>

drivers/1wire/1wire_read.c

@@ -0,0 +1,91 @@
+/****************************************************************************
+ * drivers/1wire/1wire_read.c
+ *
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.  The
+ * ASF licenses this file to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance with the
+ * License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.  See the
+ * License for the specific language governing permissions and limitations
+ * under the License.
+ *
+ ****************************************************************************/
+
+/****************************************************************************
+ * Included Files
+ ****************************************************************************/
+
+#include <nuttx/config.h>
+
+#include <assert.h>
+
+#include <nuttx/1wire/1wire.h>
+#include <nuttx/1wire/1wire_master.h>
+
+#include "1wire_internal.h"
+
+/****************************************************************************
+ * Public Functions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Name: 1wire_read
+ *
+ * Description:
+ *   Receive a block of data from 1WIRE. Each read operation will be an
+ *   'atomic' operation in the sense that any other 1WIRE actions will be
+ *   serialized and pend until this read completes.
+ *
+ * Input Parameters:
+ *   master - Device-specific state data
+ *   buffer - A pointer to a buffer of data to receive the data from the
+ *            device
+ *   buflen - The requested number of bytes to be read
+ *
+ * Returned Value:
+ *   0: success, <0: A negated errno
+ *
+ ****************************************************************************/
+
+int onewire_read(FAR struct onewire_master_s *master,
+                 FAR const struct onewire_config_s *config,
+                 FAR uint8_t *buffer, int buflen)
+{
+  int ret;
+
+  /* Avoid calling this function from a search callback to prevent a
+   * deadlock
+   */
+
+  if (master->insearch == true)
+    {
+      return -EAGAIN;
+    }
+
+  ret = onewire_sem_wait(master);
+  if (ret < 0)
+    {
+      return ret;
+    }
+
+  ret = onewire_reset_select(master, config->romcode);
+  if (ret < 0)
+    {
+      goto err_unlock;
+    }
+
+  /* Then perform the transfer. */
+
+  ret = ONEWIRE_READ(master->dev, buffer, buflen);
+
+err_unlock:
+  onewire_sem_post(master);
+  return ret;
+}