linux-kernel - [PATCH v2 5/9] char: misc: Make registering dynamic device reentry

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Message-Id: <20250701-rfc_miscdev-v2-5-3eb22bf533be@oss.qualcomm.com>
Date: Tue, 01 Jul 2025 23:24:43 +0800
From: Zijun Hu <zijun_hu@...oud.com>
To: Arnd Bergmann <arnd@...db.de>, 
 Greg Kroah-Hartman <gregkh@...uxfoundation.org>, 
 Jean Delvare <jdelvare@...e.com>, Guenter Roeck <linux@...ck-us.net>, 
 Rudolf Marek <r.marek@...embler.cz>, 
 Wim Van Sebroeck <wim@...ux-watchdog.org>, 
 "James E.J. Bottomley" <James.Bottomley@...senPartnership.com>, 
 Helge Deller <deller@....de>, "David S. Miller" <davem@...emloft.net>, 
 Andreas Larsson <andreas@...sler.com>
Cc: Thadeu Lima de Souza Cascardo <cascardo@...lia.com>, 
 Zijun Hu <zijun_hu@...oud.com>, linux-kernel@...r.kernel.org, 
 linux-hwmon@...r.kernel.org, linux-watchdog@...r.kernel.org, 
 linux-parisc@...r.kernel.org, sparclinux@...r.kernel.org, 
 Zijun Hu <zijun.hu@....qualcomm.com>
Subject: [PATCH v2 5/9] char: misc: Make registering dynamic device reentry

From: Zijun Hu <zijun.hu@....qualcomm.com>

misc_deregister() frees dynamic minor but does not reset @misc->minor
and cause kunit test case miscdev_test_dynamic_reentry() failure:

| Invalid fixed minor 257 for miscdevice 'miscdyn_a'
| #miscdev_test_dynamic_reentry: ASSERTION FAILED at misc_minor_kunit.c:639
| Expected ret == 0, but
| ret == -22 (0xffffffffffffffea)
| [FAILED] miscdev_test_dynamic_reentry

Fix by resetting dynamic minor in misc_deregister() as error handling
of misc_register() does.

Signed-off-by: Zijun Hu <zijun.hu@....qualcomm.com>
---
 drivers/char/misc.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/char/misc.c b/drivers/char/misc.c
index b8e66466184fa21fb66d968db7950e0b5669ac43..96ed343cf5c8509a09855020049a9af82a3ede95 100644
--- a/drivers/char/misc.c
+++ b/drivers/char/misc.c
@@ -288,6 +288,8 @@ void misc_deregister(struct miscdevice *misc)
 	list_del(&misc->list);
 	device_destroy(&misc_class, MKDEV(MISC_MAJOR, misc->minor));
 	misc_minor_free(misc->minor);
+	if (misc->minor > MISC_DYNAMIC_MINOR)
+		misc->minor = MISC_DYNAMIC_MINOR;
 	mutex_unlock(&misc_mtx);
 }
 EXPORT_SYMBOL(misc_deregister);

-- 
2.34.1