FS: Add logic to detach a file structure from a file descriptor. This is for use only within the OS. It permits an open file or driver to be used across multiple threads.

ChangeLog

@@ -11810,3 +11810,6 @@
 	  driver already supports a 1-wire interface, but this driver uses the
 	  same serial logic to implement a lower half driver much like the I2C
 	  lower half driver.  From Aleksandr Vyhovanec (2015-05-25).
+	* fs/: Add logic to detach a file structure from a file descriptor.
+	  This is for use only within the OS.  It permits an open file or driver
+	  to be used across multiple threads (2016-05-26).

configs/nucleo-f4x1re/src/stm32_ajoystick.c

@@ -46,6 +46,7 @@
 
 #include <nuttx/irq.h>
 #include <nuttx/arch.h>
+#include <nuttx/fs/fs.h>
 #include <nuttx/input/ajoystick.h>
 
 #include "stm32_gpio.h"
@@ -108,10 +109,6 @@
                           AJOY_BUTTON_7_BIT )
 #endif
 
-/****************************************************************************
- * Private Types
- ****************************************************************************/
-
 /****************************************************************************
  * Private Function Prototypes
  ****************************************************************************/
@@ -158,9 +155,9 @@ static const struct ajoy_lowerhalf_s g_ajoylower =
 };
 
 #ifndef NO_JOYSTICK_ADC
-/* Descriptor for the open ADC driver */
+/* Thread-independent file structure for the open ADC driver */
 
-static int g_adcfd = -1;
+static struct file g_adcfile;
 #endif
 
 /* Current interrupt handler and argument */
@@ -209,7 +206,7 @@ static int ajoy_sample(FAR const struct ajoy_lowerhalf_s *lower,
    * channels are enabled).
    */
 
-  nread = read(g_adcfd, adcmsg, MAX_ADC_CHANNELS * sizeof(struct adc_msg_s));
+  nread = file_read(&g_adcfile, adcmsg, MAX_ADC_CHANNELS * sizeof(struct adc_msg_s));
   if (nread < 0)
     {
       int errcode = get_errno();
@@ -454,6 +451,8 @@ int board_ajoy_initialize(void)
   int i;
 
 #ifndef NO_JOYSTICK_ADC
+  int fd;
+
   ivdbg("Initialize ADC driver: /dev/adc0\n");
 
   /* Initialize ADC.  We will need this to read the ADC inputs */
@@ -465,18 +464,27 @@ int board_ajoy_initialize(void)
       return ret;
     }
 
-  /* Open the ADC driver for reading.
+  /* Open the ADC driver for reading. */
-   * REVISIT:  This can't work!  The file descriptor is only valid in the
-   * task that opened the file.  Not useful for a sharable driver.
-   */
 
-  g_adcfd = open("/dev/adc0", O_RDONLY);
+  fd = open("/dev/adc0", O_RDONLY);
-  if (g_adcfd < 0)
+  if (fd < 0)
     {
       int errcode = get_errno();
       idbg("ERROR: Failed to open /dev/adc0: %d\n", errcode);
       return -errcode;
     }
+
+  /* Detach the file structure from the file descriptor so that it can be
+   * used on any thread.
+   */
+
+  ret = file_detach(fd, &g_adcfile);
+  if (ret < 0)
+    {
+      idbg("ERROR: Failed to detach from file descriptor: %d\n", ret);
+      (void)close(fd);
+      return ret;
+    }
 #endif
 
   /* Configure the GPIO pins as interrupting inputs.  NOTE: This is
@@ -500,8 +508,7 @@ int board_ajoy_initialize(void)
     {
       idbg("ERROR: ajoy_register failed: %d\n", ret);
 #ifndef NO_JOYSTICK_ADC
-      close(g_adcfd);
+      file_close_detached(&g_adcfile);
-      g_adcfd = -1;
 #endif
     }
 

configs/nucleo-l476rg/src/stm32_ajoystick.c

@@ -1,7 +1,7 @@
 /****************************************************************************
  * configs/nucleo-f3x1re/src/stm32_ajoystick.c
  *
- *   Copyright (C) 2014 Gregory Nutt. All rights reserved.
+ *   Copyright (C) 2014, 2016 Gregory Nutt. All rights reserved.
  *   Author: Gregory Nutt <gnutt@nuttx.org>
  *
  * Redistribution and use in source and binary forms, with or without
@@ -45,6 +45,7 @@
 #include <debug.h>
 
 #include <nuttx/arch.h>
+#include <nuttx/fs/fs.h>
 #include <nuttx/input/ajoystick.h>
 
 #include "stm32l4_gpio.h"
@@ -107,10 +108,6 @@
                           AJOY_BUTTON_7_BIT )
 #endif
 
-/****************************************************************************
- * Private Types
- ****************************************************************************/
-
 /****************************************************************************
  * Private Function Prototypes
  ****************************************************************************/
@@ -157,9 +154,9 @@ static const struct ajoy_lowerhalf_s g_ajoylower =
 };
 
 #ifndef NO_JOYSTICK_ADC
-/* Descriptor for the open ADC driver */
+/* Thread-independent file structure for the open ADC driver */
 
-static int g_adcfd = -1;
+static struct file g_adcfile;
 #endif
 
 /* Current interrupt handler and argument */
@@ -208,7 +205,7 @@ static int ajoy_sample(FAR const struct ajoy_lowerhalf_s *lower,
    * channels are enabled).
    */
 
-  nread = read(g_adcfd, adcmsg, MAX_ADC_CHANNELS * sizeof(struct adc_msg_s));
+  nread = file_read(&g_adcfile, adcmsg, MAX_ADC_CHANNELS * sizeof(struct adc_msg_s));
   if (nread < 0)
     {
       int errcode = get_errno();
@@ -453,6 +450,8 @@ int board_ajoy_initialize(void)
   int i;
 
 #ifndef NO_JOYSTICK_ADC
+  int fd;
+
   ivdbg("Initialize ADC driver: /dev/adc0\n");
 
   /* Initialize ADC.  We will need this to read the ADC inputs */
@@ -464,15 +463,27 @@ int board_ajoy_initialize(void)
       return ret;
     }
 
-  /* Open the ADC driver for reading */
+  /* Open the ADC driver for reading. */
 
-  g_adcfd = open("/dev/adc0", O_RDONLY);
+  fd = open("/dev/adc0", O_RDONLY);
-  if (g_adcfd < 0)
+  if (fd < 0)
     {
       int errcode = get_errno();
       idbg("ERROR: Failed to open /dev/adc0: %d\n", errcode);
       return -errcode;
     }
+
+  /* Detach the file structure from the file descriptor so that it can be
+   * used on any thread.
+   */
+
+  ret = file_detach(fd, &g_adcfile);
+  if (ret < 0)
+    {
+      idbg("ERROR: Failed to detach from file descriptor: %d\n", ret);
+      (void)close(fd);
+      return ret;
+    }
 #endif
 
   /* Configure the GPIO pins as interrupting inputs.  NOTE: This is
@@ -496,8 +507,7 @@ int board_ajoy_initialize(void)
     {
       idbg("ERROR: ajoy_register failed: %d\n", ret);
 #ifndef NO_JOYSTICK_ADC
-      close(g_adcfd);
+      file_close_detached(&g_adcfile);
-      g_adcfd = -1;
 #endif
     }
 

configs/sama5d3-xplained/src/sam_ajoystick.c

@@ -46,6 +46,7 @@
 
 #include <nuttx/irq.h>
 #include <nuttx/arch.h>
+#include <nuttx/fs/fs.h>
 #include <nuttx/input/ajoystick.h>
 
 #include "sam_pio.h"
@@ -93,10 +94,6 @@
                         AJOY_BUTTON_5_BIT | AJOY_BUTTON_6_BIT | \
                         AJOY_BUTTON_7_BIT )
 
-/****************************************************************************
- * Private Types
- ****************************************************************************/
-
 /****************************************************************************
  * Private Function Prototypes
  ****************************************************************************/
@@ -141,9 +138,9 @@ static const struct ajoy_lowerhalf_s g_ajoylower =
   .al_enable     = ajoy_enable,
 };
 
-/* Descriptor for the open ADC driver */
+/* Thread-independent file structure for the open ADC driver */
 
-static int g_adcfd = -1;
+static struct file g_adcfile;
 
 /* Current interrupt handler and argument */
 
@@ -190,7 +187,7 @@ static int ajoy_sample(FAR const struct ajoy_lowerhalf_s *lower,
    * channels are enabled).
    */
 
-  nread = read(g_adcfd, adcmsg, SAM_ADC_NCHANNELS * sizeof(struct adc_msg_s));
+  nread = file_read(&g_adcfile, adcmsg, MAX_ADC_CHANNELS * sizeof(struct adc_msg_s));
   if (nread < 0)
     {
       int errcode = get_errno();
@@ -405,6 +402,7 @@ static int ajoy_interrupt(int irq, FAR void *context)
 int sam_ajoy_initialization(void)
 {
   int ret;
+  int fd;
   int i;
 
   /* Initialize ADC.  We will need this to read the ADC inputs */
@@ -416,19 +414,28 @@ int sam_ajoy_initialization(void)
       return ret;
     }
 
-  /* Open the ADC driver for reading.
+  /* Open the ADC driver for reading. */
-   * REVISIT:  This can't work!  The file descriptor is only valid in the
-   * task that opened the file.  Not useful for a sharable driver.
-   */
 
-  g_adcfd = open("/dev/adc0", O_RDONLY);
+  fd = open("/dev/adc0", O_RDONLY);
-  if (g_adcfd < 0)
+  if (fd < 0)
     {
       int errcode = get_errno();
       idbg("ERROR: Failed to open /dev/adc0: %d\n", errcode);
       return -errcode;
     }
 
+  /* Detach the file structure from the file descriptor so that it can be
+   * used on any thread.
+   */
+
+  ret = file_detach(fd, &g_adcfile);
+  if (ret < 0)
+    {
+      idbg("ERROR: Failed to detach from file descriptor: %d\n", ret);
+      (void)close(fd);
+      return ret;
+    }
+
   /* Configure the GPIO pins as interrupting inputs. */
 
   for (i = 0; i < AJOY_NGPIOS; i++)
@@ -452,8 +459,7 @@ int sam_ajoy_initialization(void)
   if (ret < 0)
     {
       idbg("ERROR: ajoy_register failed: %d\n", ret);
-      close(g_adcfd);
+      file_close_detached(&g_adcfile);
-      g_adcfd = -1;
     }
 
   return ret;

fs/inode/Make.defs

@@ -39,7 +39,7 @@ ifneq ($(CONFIG_NFILE_DESCRIPTORS),0)
 
 CSRCS += fs_files.c fs_foreachinode.c fs_inode.c fs_inodeaddref.c
 CSRCS += fs_inodebasename.c fs_inodefind.c fs_inoderelease.c
-CSRCS += fs_inoderemove.c fs_inodereserve.c
+CSRCS += fs_inoderemove.c fs_inodereserve.c fs_filedetach.c
 
 # Include inode/utils build support
 

fs/inode/fs_filedetach.c

@@ -0,0 +1,217 @@
+/****************************************************************************
+ * fs/inode/fs_filedetach.c
+ *
+ *   Copyright (C) 2016 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 <semaphore.h>
+#include <assert.h>
+#include <errno.h>
+
+#include <nuttx/sched.h>
+#include <nuttx/fs/fs.h>
+
+#include "inode/inode.h"
+
+/****************************************************************************
+ * Private Functions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Name: _files_semtake
+ ****************************************************************************/
+
+static inline void _files_semtake(FAR struct filelist *list)
+{
+  /* Take the semaphore (perhaps waiting) */
+
+  while (sem_wait(&list->fl_sem) != 0)
+    {
+      /* The only case that an error should occur here is if
+       * the wait was awakened by a signal.
+       */
+
+      DEBUGASSERT(get_errno() == EINTR);
+    }
+}
+
+/****************************************************************************
+ * Name: _files_semgive
+ ****************************************************************************/
+
+#define _files_semgive(list) sem_post(&list->fl_sem)
+
+/****************************************************************************
+ * Public Functions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Name: file_detach
+ *
+ * Description:
+ *   This function is used to device drivers to create a task-independent
+ *   handle to an entity in the file system.  file_detach() duplicates the
+ *   'struct file' that underlies the file descriptor, then closes the file
+ *   descriptor.
+ *
+ *   This function will fail if fd is not a valid file descriptor.  In
+ *   particular, it will fail if fd is a socket descriptor.
+ *
+ * Input Parameters:
+ *   fd    - The file descriptor to be detached.  This descriptor will be
+ *           closed and invalid if the file was successfully detached.
+ *   filep - A pointer to a user provided memory location in which to
+ *           received the duplicated, detached file structure.
+ *
+ * Returned Value:
+ *   Zero (OK) is returned on success; A negated errno value is returned on
+ *   any failure to indicate the nature of the failure.
+ *
+ ****************************************************************************/
+
+#if CONFIG_NFILE_DESCRIPTORS > 0
+int file_detach(int fd, FAR struct file *filep)
+{
+  FAR struct filelist *list;
+  FAR struct file *parent;
+
+  /* Verify the file descriptor range */
+
+  if (fd < 0 || fd >= CONFIG_NFILE_DESCRIPTORS)
+    {
+      /* Not a file descriptor (might be a socket descriptor) */
+
+      return -EBADF;
+    }
+
+  /* Get the thread-specific file list.  It should never be NULL in this
+   * context.
+   */
+
+  list = sched_getfiles();
+  DEBUGASSERT(list != NULL);
+
+  /* If the file was properly opened, there should be an inode assigned */
+
+  _files_semtake(list);
+  parent = &list->fl_files[fd];
+  if (parent->f_inode == NULL)
+    {
+      /* File is not open */
+
+      _files_semgive(list);
+      return -EBADF;
+    }
+
+  /* Duplicate the 'struct file' content into the user-provided file
+   * structure.
+   */
+
+  filep->f_oflags  = parent->f_oflags;
+  filep->f_pos     = parent->f_pos;
+  filep->f_inode   = parent->f_inode;
+  filep->f_priv    = parent->f_priv;
+
+  /* Release the file descriptore *without* calling the drive close method
+   * and without decrementing the inode reference count.  That will be done
+   * in file_close_detached().
+   */
+
+  parent->f_oflags = 0;
+  parent->f_pos    = 0;
+  parent->f_inode  = NULL;
+  parent->f_priv   = NULL;
+
+  _files_semgive(list);
+  return OK;
+}
+#endif
+
+/****************************************************************************
+ * Name: file_close_detached
+ *
+ * Description:
+ *   Close a file that was previously detached with file_detach().
+ *
+ *   REVISIT:  This is essentially the same as _files_close()
+ *
+ * Input Parameters:
+ *   filep - A pointer to a user provided memory location containing the
+ *           open file data returned by file_detach().
+ *
+ * Returned Value:
+ *   Zero (OK) is returned on success; A negated errno value is returned on
+ *   any failure to indicate the nature of the failure.
+ *
+ ****************************************************************************/
+
+int file_close_detached(FAR struct file *filep)
+{
+  struct inode *inode;
+  int ret = OK;
+
+  DEBUGASSERT(filep != NULL);
+  inode = filep->f_inode;
+
+  /* Check if the struct file is open (i.e., assigned an inode) */
+
+  if (inode)
+    {
+      /* Close the file, driver, or mountpoint. */
+
+      if (inode->u.i_ops && inode->u.i_ops->close)
+        {
+          /* Perform the close operation */
+
+          ret = inode->u.i_ops->close(filep);
+        }
+
+      /* And release the inode */
+
+      inode_release(inode);
+
+      /* Reset the user file struct instance so that it cannot be reused. */
+
+      filep->f_oflags = 0;
+      filep->f_pos    = 0;
+      filep->f_inode  = NULL;
+      filep->f_priv   = NULL;
+    }
+
+  return ret;
+}

fs/inode/fs_files.c

@@ -65,7 +65,7 @@ static void _files_semtake(FAR struct filelist *list)
 
   while (sem_wait(&list->fl_sem) != 0)
     {
-      /* The only case that an error should occr here is if
+      /* The only case that an error should occur here is if
        * the wait was awakened by a signal.
        */
 
@@ -362,9 +362,9 @@ int files_close(int fd)
   /* If the file was properly opened, there should be an inode assigned */
 
   if (fd < 0 || fd >= CONFIG_NFILE_DESCRIPTORS || !list->fl_files[fd].f_inode)
-   {
+    {
-     return -EBADF;
+      return -EBADF;
-   }
+    }
 
   /* Perform the protected close operation */
 

fs/vfs/fs_close.c

@@ -105,7 +105,7 @@ int close(int fd)
 
 #if CONFIG_NFILE_DESCRIPTORS > 0
   /* Close the driver or mountpoint.  NOTES: (1) there is no
-   * exclusion mechanism here , the driver or mountpoint must be
+   * exclusion mechanism here, the driver or mountpoint must be
    * able to handle concurrent operations internally, (2) The driver
    * may have been opened numerous times (for different file
    * descriptors) and must also handle being closed numerous times.

include/nuttx/fs/fs.h

@@ -532,7 +532,7 @@ int file_dup2(FAR struct file *filep1, FAR struct file *filep2);
  *   function IS dup().
  *
  *   This alternative naming is used when dup could operate on both file and
- *   socket descritors to avoid drawing unused socket support into the link.
+ *   socket descriptors to avoid drawing unused socket support into the link.
  *
  ****************************************************************************/
 
@@ -574,6 +574,52 @@ int fs_dupfd2(int fd1, int fd2);
 #endif
 #endif
 
+/****************************************************************************
+ * Name: file_detach
+ *
+ * Description:
+ *   This function is used to device drivers to create a task-independent
+ *   handle to an entity in the file system.  file_detach() duplicates the
+ *   'struct file' that underlies the file descriptor, then closes the file
+ *   descriptor.
+ *
+ *   This function will fail if fd is not a valid file descriptor.  In
+ *   particular, it will fail if fd is a socket descriptor.
+ *
+ * Input Parameters:
+ *   fd    - The file descriptor to be detached.  This descriptor will be
+ *           closed and invalid if the file was successfully detached.
+ *   filep - A pointer to a user provided memory location in which to
+ *           received the duplicated, detached file structure.
+ *
+ * Returned Value:
+ *   Zero (OK) is returned on success; A negated errno value is returned on
+ *   any failure to indicate the nature of the failure.
+ *
+ ****************************************************************************/
+
+#if CONFIG_NFILE_DESCRIPTORS > 0
+int file_detach(int fd, FAR struct file *filep);
+#endif
+
+/****************************************************************************
+ * Name: file_close_detached
+ *
+ * Description:
+ *   Close a file that was previously detached with file_detach().
+ *
+ * Input Parameters:
+ *   filep - A pointer to a user provided memory location containing the
+ *           open file data returned by file_detach().
+ *
+ * Returned Value:
+ *   Zero (OK) is returned on success; A negated errno value is returned on
+ *   any failure to indicate the nature of the failure.
+ *
+ ****************************************************************************/
+
+int file_close_detached(FAR struct file *filep);
+
 /****************************************************************************
  * Name: open_blockdriver
  *