Staging: comedi: Allow 'open' driver method to fail

Some comedi drivers should return an error from their 'open' method when
something goes wrong.  Change the prototype of the 'open' method in
'struct comedi_device' to allow this, and change the drivers that use it.
Propagate any error to the 'open' file operation.

The corresponding 'close' method won't be called when the 'open' method
fails, so drivers failing the 'open' need to clean up any mess they
created.

The dt9812 and serial2002 drivers can now return an error on 'open'.
The jr3_pci driver also uses the 'open' method but doesn't fail it.

Signed-off-by: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/staging/comedi/comedi_fops.c

@@ -1845,8 +1845,15 @@ static int comedi_open(struct inode *inode, struct file *file)
 		}
 	}
 
-	if (dev->attached && dev->use_count == 0 && dev->open)
-		dev->open(dev);
+	if (dev->attached && dev->use_count == 0 && dev->open) {
+		int rc = dev->open(dev);
+		if (rc < 0) {
+			module_put(dev->driver->module);
+			module_put(THIS_MODULE);
+			mutex_unlock(&dev->mutex);
+			return rc;
+		}
+	}
 
 	dev->use_count++;
 

drivers/staging/comedi/comedidev.h

@@ -285,7 +285,7 @@ struct comedi_device {
 
 	struct fasync_struct *async_queue;
 
-	void (*open) (struct comedi_device *dev);
+	int (*open) (struct comedi_device *dev);
 	void (*close) (struct comedi_device *dev);
 };
 

drivers/staging/comedi/drivers/dt9812.c

@@ -890,8 +890,10 @@ static struct usb_driver dt9812_usb_driver = {
  * Comedi functions
  */
 
-static void dt9812_comedi_open(struct comedi_device *dev)
+static int dt9812_comedi_open(struct comedi_device *dev)
 {
+	int result = -ENODEV;
+
 	down(&devpriv->slot->mutex);
 	if (devpriv->slot->usb) {
 		/* We have an attached device, fill in current range info */
@@ -934,8 +936,10 @@ static void dt9812_comedi_open(struct comedi_device *dev)
 			}
 			break;
 		}
+		result = 0;
 	}
 	up(&devpriv->slot->mutex);
+	return result;
 }
 
 static int dt9812_di_rinsn(struct comedi_device *dev,

drivers/staging/comedi/drivers/jr3_pci.c

@@ -373,7 +373,7 @@ static int jr3_pci_ai_insn_read(struct comedi_device *dev,
 	return result;
 }
 
-static void jr3_pci_open(struct comedi_device *dev)
+static int jr3_pci_open(struct comedi_device *dev)
 {
 	int i;
 	struct jr3_pci_dev_private *devpriv = dev->private;
@@ -388,6 +388,7 @@ static void jr3_pci_open(struct comedi_device *dev)
 			       p->channel_no);
 		}
 	}
+	return 0;
 }
 
 int read_idm_word(const u8 * data, size_t size, int *pos, unsigned int *val)

drivers/staging/comedi/drivers/serial2002.c

@@ -393,15 +393,16 @@ static void serial_write(struct file *f, struct serial_data data)
 	}
 }
 
-static void serial_2002_open(struct comedi_device *dev)
+static int serial_2002_open(struct comedi_device *dev)
 {
+	int result;
 	char port[20];
 
 	sprintf(port, "/dev/ttyS%d", devpriv->port);
 	devpriv->tty = filp_open(port, O_RDWR, 0);
 	if (IS_ERR(devpriv->tty)) {
-		printk("serial_2002: file open error = %ld\n",
-		       PTR_ERR(devpriv->tty));
+		result = (int)PTR_ERR(devpriv->tty);
+		printk("serial_2002: file open error = %d\n", result);
 	} else {
 		struct config_t {
 
@@ -673,7 +674,9 @@ static void serial_2002_open(struct comedi_device *dev)
 				}
 			}
 		}
+		result = 0;
 	}
+	return result;
 }
 
 static void serial_2002_close(struct comedi_device *dev)