drivers/can/can.c: Fix errors with pointers when using internal OS in…

…terface (#118)

* Fix CAN driver to work with internal OS interfaces.  Store internal file pointer in f_priv and use it then to distinct readers (See issue #111)
* Store reader pointer in f_priv instead of filep
* Don't need in filep in can_reader_s

drivers/can/can.c

@@ -390,7 +390,7 @@ static FAR struct can_reader_s *init_can_reader(FAR struct file *filep)
  reader->fifo.rx_tail = 0;
 
  nxsem_init(&reader->fifo.rx_sem, 0, 1);
- reader->filep = filep;
+ filep->f_priv = reader;
 
  return reader;
 }
@@ -509,14 +509,16 @@ static int can_close(FAR struct file *filep)
 
  list_for_every_safe(&dev->cd_readers, node, tmp)
  {
- if (((FAR struct can_reader_s *)node)->filep == filep)
+ if (((FAR struct can_reader_s *)node) == ((FAR struct can_reader_s *)filep->f_priv))
  {
  list_delete(node);
  kmm_free(node);
  break;
  }
  }
 
+ filep->f_priv = NULL;
+
  /* Decrement the references to the driver. If the reference count will
  * decrement to 0, then uninitialize the driver.
  */
@@ -574,7 +576,6 @@ static ssize_t can_read(FAR struct file *filep, FAR char *buffer,
  FAR struct inode *inode = filep->f_inode;
  FAR struct can_dev_s *dev = inode->i_private;
  FAR struct can_reader_s *reader = NULL;
- FAR struct list_node *node;
  FAR struct can_rxfifo_s *fifo;
  size_t nread;
  irqstate_t flags;
@@ -630,16 +631,8 @@ static ssize_t can_read(FAR struct file *filep, FAR char *buffer,
  }
 #endif /* CONFIG_CAN_ERRORS */
 
- list_for_every(&dev->cd_readers, node)
- {
- if (((FAR struct can_reader_s *) node)->filep == filep)
- {
- reader = (FAR struct can_reader_s *)node;
- break;
- }
- }
-
- DEBUGASSERT(reader != NULL);
+ DEBUGASSERT(filep->f_priv != NULL);
+ reader = (FAR struct can_reader_s *)filep->f_priv;
 
  fifo = &reader->fifo;
 
@@ -1027,7 +1020,6 @@ static int can_poll(FAR struct file *filep, FAR struct pollfd *fds,
  FAR struct inode *inode = (FAR struct inode *)filep->f_inode;
  FAR struct can_dev_s *dev = (FAR struct can_dev_s *)inode->i_private;
  FAR struct can_reader_s *reader = NULL;
- FAR struct list_node *node;
  pollevent_t eventset;
  int ndx;
  int ret;
@@ -1042,16 +1034,8 @@ static int can_poll(FAR struct file *filep, FAR struct pollfd *fds,
  }
 #endif
 
- list_for_every(&dev->cd_readers, node)
- {
- if (((FAR struct can_reader_s *)node)->filep == filep)
- {
- reader = (FAR struct can_reader_s *)node;
- break;
- }
- }
-
- DEBUGASSERT(reader != NULL);
+ DEBUGASSERT(filep->f_priv != NULL);
+ reader = (FAR struct can_reader_s *)filep->f_priv;
 
  /* Get exclusive access to the poll structures */
 

include/nuttx/can/can.h

@@ -561,7 +561,6 @@ struct can_reader_s
 {
  struct list_node list;
  sem_t read_sem;
- FAR struct file *filep;
  struct can_rxfifo_s fifo; /* Describes receive FIFO */
 };