staging: comedi: comedi_fops: introduce comedi_dev_from_minor()

A number of functions have to call comedi_get_device_file_info()
to get the comedi_device_file_info pointer for a given minor. That
pointer is only used to get the actual comedi_device pointer for
the minor.

Introduce a new helper function, comedi_dev_from_minor(), to simplify
this operation. This will also allow us to make the comedi_device_file_info
struct private.

Signed-off-by: H Hartley Sweeten <[e-mail]>
Cc: Ian Abbott <[e-mail]>
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

drivers/staging/comedi/comedi_fops.c

···
 static struct comedi_device_file_info
 *comedi_file_info_table[COMEDI_NUM_MINORS];
 
+struct comedi_device *comedi_dev_from_minor(unsigned minor)
+{
+	struct comedi_device_file_info *info;
+
+	info = comedi_get_device_file_info(minor);
+
+	return info ? info->device : NULL;
+}
+EXPORT_SYMBOL_GPL(comedi_dev_from_minor);
+
 static struct comedi_subdevice *
 comedi_get_read_subdevice(const struct comedi_device_file_info *info)
 {

drivers/staging/comedi/comedidev.h

···
 
 struct comedi_device_file_info *comedi_get_device_file_info(unsigned minor);
 
+struct comedi_device *comedi_dev_from_minor(unsigned minor);
+
 int comedi_alloc_subdevices(struct comedi_device *, int);
 
 void comedi_device_detach(struct comedi_device *dev);