[PATCH 4.9 53/88] parport: fix attempt to write duplicate procfiles

[Greg Kroah-Hartman]

4.9-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Sudip Mukherjee <sudipm.mukherjee@xxxxxxxxx>

commit 03270c6ac6207fc55bbf9d20d195029dca210c79 upstream.

Usually every parallel port will have a single pardev registered with
it. But ppdev driver is an exception. This userspace parallel port
driver allows to create multiple parrallel port devices for a single
parallel port. And as a result we were having a nice warning like:
"sysctl table check failed:
/dev/parport/parport0/devices/ppdev0/timeslice Sysctl already exists"

Use the same logic as used in parport_register_device() and register
the proc files only once for each parallel port.

Fixes: 6fa45a226897 ("parport: add device-model to parport subsystem")
Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=1414656
Bugzilla: https://bugs.archlinux.org/task/52322
Tested-by: James Feeney <james@xxxxxxxxxxx>
Signed-off-by: Sudip Mukherjee <sudip.mukherjee@xxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 drivers/parport/share.c |    6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

--- a/drivers/parport/share.c
+++ b/drivers/parport/share.c
@@ -939,8 +939,10 @@ parport_register_dev_model(struct parpor
 	 * pardevice fields. -arca
 	 */
 	port->ops->init_state(par_dev, par_dev->state);
-	port->proc_device = par_dev;
-	parport_device_proc_register(par_dev);
+	if (!test_and_set_bit(PARPORT_DEVPROC_REGISTERED, &port->devflags)) {
+		port->proc_device = par_dev;
+		parport_device_proc_register(par_dev);
+	}
 
 	return par_dev;