drivers/loop: Add a loop character device that can be used to setup and teardown loop devices

drivers/loop/loop.c

@@ -0,0 +1,179 @@
+/****************************************************************************
+ * drivers/loop/loop.c
+ *
+ *   Copyright (C) 2015 Gregory Nutt. All rights reserved.
+ *   Author: Gregory Nutt <gnutt@nuttx.org>
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ * 3. Neither the name NuttX nor the names of its contributors may be
+ *    used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
+ * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ *
+ ****************************************************************************/
+
+/****************************************************************************
+ * Included Files
+ ****************************************************************************/
+
+#include <nuttx/config.h>
+
+#include <sys/types.h>
+#include <stdbool.h>
+#include <string.h>
+#include <errno.h>
+
+#include <nuttx/fs/fs.h>
+#include <nuttx/fs/loop.h>
+
+#ifdef CONFIG_DEV_LOOP
+
+/****************************************************************************
+ * Private Function Prototypes
+ ****************************************************************************/
+
+static ssize_t loop_read(FAR struct file *filep, FAR char *buffer,
+                 size_t buflen);
+static ssize_t loop_write(FAR struct file *filep, FAR const char *buffer,
+                 size_t buflen);
+static int     loop_ioctl(FAR struct file *filep, int cmd, unsigned long arg);
+
+/****************************************************************************
+ * Private Data
+ ****************************************************************************/
+
+static const struct file_operations loop_fops =
+{
+  0,             /* open */
+  0,             /* close */
+  loop_read,     /* read */
+  loop_write,    /* write */
+  0,             /* seek */
+  loop_ioctl     /* ioctl */
+#ifndef CONFIG_DISABLE_POLL
+  , 0            /* poll */
+#endif
+};
+
+/****************************************************************************
+ * Private Functions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Name: loop_read
+ ****************************************************************************/
+
+static ssize_t loop_read(FAR struct file *filep, FAR char *buffer, size_t len)
+{
+  return 0; /* Return EOF */
+}
+
+/****************************************************************************
+ * Name: loop_write
+ ****************************************************************************/
+
+static ssize_t loop_write(FAR struct file *filep, FAR const char *buffer, size_t len)
+{
+  return len; /* Say that everything was written */
+}
+
+/****************************************************************************
+ * Name: loop_ioctl
+ ****************************************************************************/
+
+static int loop_ioctl(FAR struct file *filep, int cmd, unsigned long arg)
+{
+  int ret;
+
+  switch (cmd)
+    {
+    /* Command:      LOOPIOC_SETUP
+     * Description:  Setup the loop device
+     * Argument:     A pointer to a read-only instance of struct losetup_s.
+     * Dependencies: The loop device must be enabled (CONFIG_DEV_LOOP=y)
+     */
+
+    case LOOPIOC_SETUP:
+      {
+         FAR struct losetup_s *setup = (FAR struct losetup_s *)((uintptr_t)arg);
+
+        if (setup == NULL)
+          {
+            ret = -EINVAL;
+          }
+        else
+          {
+            ret = losetup(setup->devname, setup->filename, setup->sectsize,
+                         setup->offset, setup->readonly);
+          }
+      }
+      break;
+
+    /* Command:      LOOPIOC_TEARDOWN
+     * Description:  Teardown a loop device previously setup vis LOOPIOC_SETUP
+     * Argument:     A read-able pointer to the path of the device to be
+     *               torn down
+     * Dependencies: The loop device must be enabled (CONFIG_DEV_LOOP=y)
+     */
+
+    case LOOPIOC_TEARDOWN:
+      {
+        FAR const char *devname = (FAR const char *)((uintptr_t)arg);
+
+        if (devname == NULL)
+          {
+            ret = -EINVAL;
+          }
+        else
+          {
+            ret = loteardown(devname);
+          }
+       }
+       break;
+
+     default:
+       ret = -ENOTTY;
+    }
+
+  return ret;
+}
+
+/****************************************************************************
+ * Public Functions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Name: loop_register
+ *
+ * Description:
+ *   Register /dev/null
+ *
+ ****************************************************************************/
+
+void loop_register(void)
+{
+  (void)register_driver("/dev/loop", &loop_fops, 0666, NULL);
+}
+
+#endif /* CONFIG_DEV_LOOP */