linux-kernel - [PATCH] hid: Register debugfs entries before adding device

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Message-ID: <20100313231355.61c75c30@neptune.home>
Date:	Sat, 13 Mar 2010 23:13:55 +0100
From:	Bruno Prémont <bonbons@...ux-vserver.org>
To:	Alan Stern <stern@...land.harvard.edu>,
	Jiri Kosina <jkosina@...e.cz>
Cc:	<linux-input@...r.kernel.org>, <linux-usb@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>,
	"Rick L. Vinyard Jr." <rvinyard@...nmsu.edu>,
	Nicu Pavel <npavel@...ner.com>
Subject: [PATCH] hid: Register debugfs entries before adding device

On Sat, 13 March 2010 Alan Stern <stern@...land.harvard.edu> wrote:
> 
> If the device_add() fails, you should undo the hid_debug_register() 
> call.

Well I was wondering why hid_debug_register() was called no matter what
device_add() returned but didn't dig around what happened when
hid_add_device() would return an error.

Looking a few lines further, hid_remove_device() just unregisters debugfs
entries when status has HID_STAT_ADDED so it definitely makes sense to
do the proper cleanup (and hid_remove_device() is the only once calling
hid_debug_unregister())

So patch for both below:




Register debugfs entries before calling device_add() so debugfs entries
are already present when HID driver's probe function gets called on device
hotplug.
Also undo debugfs entry registration if device_add() fails so status
HID_STAT_ADDED and debugfs registration status remain consistent and
we don't leak the debugfs entries.

Signed-off-by: Bruno Prémont <bonbons@...ux-vserver.org>
Cc: Alan Stern <stern@...land.harvard.edu>
---


diff --git a/drivers/hid/hid-core.c b/drivers/hid/hid-core.c
index eabe5f8..709b4d0 100644
--- a/drivers/hid/hid-core.c
+++ b/drivers/hid/hid-core.c
@@ -1759,11 +1759,12 @@ int hid_add_device(struct hid_device *hdev)
 	dev_set_name(&hdev->dev, "%04X:%04X:%04X.%04X", hdev->bus,
 		     hdev->vendor, hdev->product, atomic_inc_return(&id));
 
+	hid_debug_register(hdev, dev_name(&hdev->dev));
 	ret = device_add(&hdev->dev);
 	if (!ret)
 		hdev->status |= HID_STAT_ADDED;
-
-	hid_debug_register(hdev, dev_name(&hdev->dev));
+	else
+		hid_debug_unregister(hdev);
 
 	return ret;
 }
--
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