Patch "ppdev: fix registering same device name" has been added to the 4.10-stable tree

This is a note to let you know that I've just added the patch titled

ppdev: fix registering same device name

to the 4.10-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
ppdev-fix-registering-same-device-name.patch
and it can be found in the queue-4.10 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Sudip Mukherjee <[email protected]>
Date: Mon, 6 Mar 2017 23:23:43 +0000
Subject: ppdev: fix registering same device name

From: Sudip Mukherjee <[email protected]>

commit 9a69645dde1188723d80745c1bc6ee9af2cbe2a7 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 big warning like:
"sysfs: cannot create duplicate filename '/devices/parport0/ppdev0.0'". And with that many parallel port printers stopped working.

We have been using the minor number as the id field while registering a parralel port device with a parralel port. But when there are multiple parrallel port device for one single parallel port, they all tried to register with the same name like 'pardev0.0' and everything started failing.
Use an incremented index as the id instead of the minor number.

Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=1414656
Bugzilla: https://bugs.archlinux.org/task/52322

---
 drivers/char/ppdev.c |   11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

@@ -84,11 +84,14 @@ struct pp_struct {
 	struct ieee1284_info state;
 	struct ieee1284_info saved_state;
 	long default_inactivity;
+	int index;
 };
 
 /* should we use PARDEVICE_MAX here? */
 static struct device *devices[PARPORT_MAX];
 
+static DEFINE_IDA(ida_index);
+
 /* pp_struct.flags bitfields */
 #define PP_CLAIMED    (1<<0)
 #define PP_EXCL       (1<<1)

@@ -290,7 +293,7 @@ static int register_device(int minor, st
 	struct pardevice *pdev = NULL;
 	char *name;
 	struct pardev_cb ppdev_cb;
-	int rc = 0;
+	int rc = 0, index;
 
 	name = kasprintf(GFP_KERNEL, CHRDEV "%x", minor);
 	if (name == NULL)

@@ -303,20 +306,23 @@ static int register_device(int minor, st
 		goto err;
 	}
 
+	index = ida_simple_get(&ida_index, 0, 0, GFP_KERNEL);
 	memset(&ppdev_cb, 0, sizeof(ppdev_cb));
 	ppdev_cb.irq_func = pp_irq;
 	ppdev_cb.flags = (pp->flags & PP_EXCL) ? PARPORT_FLAG_EXCL : 0;
 	ppdev_cb.private = pp;
-	pdev = parport_register_dev_model(port, name, &ppdev_cb, minor);
+	pdev = parport_register_dev_model(port, name, &ppdev_cb, index);
 	parport_put_port(port);
 
 	if (!pdev) {
 		pr_warn("%s: failed to register device!\n", name);
 		rc = -ENXIO;
+		ida_simple_remove(&ida_index, index);
 		goto err;
 	}
 
 	pp->pdev = pdev;
+	pp->index = index;
 	dev_dbg(&pdev->dev, "registered pardevice\n");
 err:
 	kfree(name);

@@ -755,6 +761,7 @@ static int pp_release(struct inode *inod
 
 	if (pp->pdev) {
 		parport_unregister_device(pp->pdev);
+		ida_simple_remove(&ida_index, pp->index);
 		pp->pdev = NULL;
 		pr_debug(CHRDEV "%x: unregistered pardevice\n", minor);
 	}

Patches currently in stable-queue which might be from [email protected] are

queue-4.10/parport-fix-attempt-to-write-duplicate-procfiles.patch queue-4.10/ppdev-fix-registering-same-device-name.patch