parport: fix attempt to write duplicate procfiles

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")
Cc: stable <stable@vger.kernel.org> # v4.4+
Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=1414656
Bugzilla: https://bugs.archlinux.org/task/52322
Tested-by: James Feeney <james@nurealm.net>
Signed-off-by: Sudip Mukherjee <sudip.mukherjee@codethink.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 4 insertions, 2 deletions

diff --git a/drivers/parport/share.c b/drivers/parport/share.c
index bc090daa850a..5dc53d420ca8 100644
--- a/drivers/parport/share.c
+++ b/drivers/parport/share.c
@@ -939,8 +939,10 @@ parport_register_dev_model(struct parport *port, const char *name,
          * 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;