linux-kernel - [PATCH v4 2/8] char: misc: Adapt and add test cases for simple minor space division

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Message-Id: <20250704-rfc_miscdev-v4-2-b48986112d6a@oss.qualcomm.com>
Date: Fri, 04 Jul 2025 21:26:00 +0800
From: Zijun Hu <zijun_hu@...oud.com>
To: Arnd Bergmann <arnd@...db.de>, 
 Greg Kroah-Hartman <gregkh@...uxfoundation.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-parisc@...r.kernel.org, sparclinux@...r.kernel.org, 
 Zijun Hu <zijun.hu@....qualcomm.com>
Subject: [PATCH v4 2/8] char: misc: Adapt and add test cases for simple
 minor space division

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

Adapt and add test cases for next change which Regards minor
which > MISC_DYNAMIC_MINOR as invalid parameter when register
miscdevice, hence get a simple minor space division below:

|<  255 : Fixed minor code
|== 255 : Indicator to request dynamic minor code
|>  255 : Dynamic minor code requested, 1048320 minor codes totally.

Signed-off-by: Zijun Hu <zijun.hu@....qualcomm.com>
---
 drivers/char/misc_minor_kunit.c | 51 +++++++++++++++++------------------------
 1 file changed, 21 insertions(+), 30 deletions(-)

diff --git a/drivers/char/misc_minor_kunit.c b/drivers/char/misc_minor_kunit.c
index 30eceac5f1b6402b0f918af6f56602ed1a6c14ec..3184f383bea8c77cbca69ff5e315ea5de2d5512e 100644
--- a/drivers/char/misc_minor_kunit.c
+++ b/drivers/char/misc_minor_kunit.c
@@ -7,12 +7,6 @@
 #include <linux/file.h>
 #include <linux/init_syscalls.h>
 
-/* dynamic minor (2) */
-static struct miscdevice dev_dynamic_minor = {
-	.minor  = 2,
-	.name   = "dev_dynamic_minor",
-};
-
 /* static minor (LCD_MINOR) */
 static struct miscdevice dev_static_minor = {
 	.minor  = LCD_MINOR,
@@ -25,16 +19,6 @@ static struct miscdevice dev_misc_dynamic_minor = {
 	.name   = "dev_misc_dynamic_minor",
 };
 
-static void kunit_dynamic_minor(struct kunit *test)
-{
-	int ret;
-
-	ret = misc_register(&dev_dynamic_minor);
-	KUNIT_EXPECT_EQ(test, 0, ret);
-	KUNIT_EXPECT_EQ(test, 2, dev_dynamic_minor.minor);
-	misc_deregister(&dev_dynamic_minor);
-}
-
 static void kunit_static_minor(struct kunit *test)
 {
 	int ret;
@@ -157,13 +141,7 @@ static bool is_valid_dynamic_minor(int minor)
 {
 	if (minor < 0)
 		return false;
-	if (minor == MISC_DYNAMIC_MINOR)
-		return false;
-	if (minor >= 0 && minor <= 15)
-		return false;
-	if (minor >= 128 && minor < MISC_DYNAMIC_MINOR)
-		return false;
-	return true;
+	return minor > MISC_DYNAMIC_MINOR;
 }
 
 static int miscdev_test_open(struct inode *inode, struct file *file)
@@ -557,7 +535,7 @@ static void __init miscdev_test_conflict(struct kunit *test)
 	 */
 	miscstat.minor = miscdyn.minor;
 	ret = misc_register(&miscstat);
-	KUNIT_EXPECT_EQ(test, ret, -EBUSY);
+	KUNIT_EXPECT_EQ(test, ret, -EINVAL);
 	if (ret == 0)
 		misc_deregister(&miscstat);
 
@@ -590,8 +568,9 @@ static void __init miscdev_test_conflict_reverse(struct kunit *test)
 	misc_deregister(&miscdyn);
 
 	ret = misc_register(&miscstat);
-	KUNIT_EXPECT_EQ(test, ret, 0);
-	KUNIT_EXPECT_EQ(test, miscstat.minor, miscdyn.minor);
+	KUNIT_EXPECT_EQ(test, ret, -EINVAL);
+	if (ret == 0)
+		misc_deregister(&miscstat);
 
 	/*
 	 * Try to register a dynamic minor after registering a static minor
@@ -601,20 +580,32 @@ static void __init miscdev_test_conflict_reverse(struct kunit *test)
 	miscdyn.minor = MISC_DYNAMIC_MINOR;
 	ret = misc_register(&miscdyn);
 	KUNIT_EXPECT_EQ(test, ret, 0);
-	KUNIT_EXPECT_NE(test, miscdyn.minor, miscstat.minor);
+	KUNIT_EXPECT_EQ(test, miscdyn.minor, miscstat.minor);
 	KUNIT_EXPECT_TRUE(test, is_valid_dynamic_minor(miscdyn.minor));
 	if (ret == 0)
 		misc_deregister(&miscdyn);
+}
 
-	miscdev_test_can_open(test, &miscstat);
+/* Take minor(> MISC_DYNAMIC_MINOR) as invalid when register miscdevice */
+static void miscdev_test_invalid_input(struct kunit *test)
+{
+	struct miscdevice misc_test = {
+		.minor = MISC_DYNAMIC_MINOR + 1,
+		.name = "misc_test",
+		.fops = &miscdev_test_fops,
+	};
+	int ret;
 
-	misc_deregister(&miscstat);
+	ret = misc_register(&misc_test);
+	KUNIT_EXPECT_EQ(test, ret, -EINVAL);
+	if (ret == 0)
+		misc_deregister(&misc_test);
 }
 
 static struct kunit_case test_cases[] = {
-	KUNIT_CASE(kunit_dynamic_minor),
 	KUNIT_CASE(kunit_static_minor),
 	KUNIT_CASE(kunit_misc_dynamic_minor),
+	KUNIT_CASE(miscdev_test_invalid_input),
 	KUNIT_CASE_PARAM(miscdev_test_twice, miscdev_gen_params),
 	KUNIT_CASE_PARAM(miscdev_test_duplicate_minor, miscdev_gen_params),
 	KUNIT_CASE(miscdev_test_duplicate_name),

-- 
2.34.1