Using guard notation makes the code more compact and error handling
more robust by ensuring that mutexes are released in all code paths
when control leaves critical section.

Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
---
 drivers/input/keyboard/maple_keyb.c | 9 ++-------
 1 file changed, 2 insertions(+), 7 deletions(-)

diff --git a/drivers/input/keyboard/maple_keyb.c b/drivers/input/keyboard/maple_keyb.c
index 91a1d2958109..fca7df1e3ae3 100644
--- a/drivers/input/keyboard/maple_keyb.c
+++ b/drivers/input/keyboard/maple_keyb.c
@@ -132,14 +132,11 @@ static void dc_kbd_callback(struct mapleq *mq)
 	 * We should always get the lock because the only
 	 * time it may be locked is if the driver is in the cleanup phase.
 	 */
-	if (likely(mutex_trylock(&maple_keyb_mutex))) {
-
+	scoped_guard(mutex_try, &maple_keyb_mutex) {
 		if (buf[1] == mapledev->function) {
 			memcpy(kbd->new, buf + 2, 8);
 			dc_scan_kbd(kbd);
 		}
-
-		mutex_unlock(&maple_keyb_mutex);
 	}
 }
 
@@ -211,14 +208,12 @@ static int remove_maple_kbd(struct device *dev)
 	struct maple_device *mdev = to_maple_dev(dev);
 	struct dc_kbd *kbd = maple_get_drvdata(mdev);
 
-	mutex_lock(&maple_keyb_mutex);
+	guard(mutex, &maple_keyb_mutex);
 
 	input_unregister_device(kbd->dev);
 	kfree(kbd);
 
 	maple_set_drvdata(mdev, NULL);
-
-	mutex_unlock(&maple_keyb_mutex);
 	return 0;
 }
 
-- 
2.47.0.163.g1226f6d8fa-goog


-- 
Dmitry

Hi Dmitry,

kernel test robot noticed the following build errors:

[auto build test ERROR on dtor-input/next]
[also build test ERROR on dtor-input/for-linus hid/for-next linus/master v6.12-rc4 next-20241025]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/Dmitry-Torokhov/Input-maple_keyb-use-guard-notation-when-acquiring-mutex/20241025-094751
base:   https://git.kernel.org/pub/scm/linux/kernel/git/dtor/input.git next
patch link:    https://lore.kernel.org/r/Zxr4TeGwDGIIyzwH%40google.com
patch subject: [PATCH] Input: maple_keyb - use guard notation when acquiring mutex
config: sh-dreamcast_defconfig (https://download.01.org/0day-ci/archive/20241026/202410261312.femv4WzA-lkp@intel.com/config)
compiler: sh4-linux-gcc (GCC) 13.3.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20241026/202410261312.femv4WzA-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202410261312.femv4WzA-lkp@intel.com/

All errors (new ones prefixed by >>):

   drivers/input/keyboard/maple_keyb.c: In function 'remove_maple_kbd':
>> drivers/input/keyboard/maple_keyb.c:211:39: error: macro "guard" passed 2 arguments, but takes just 1
     211 |         guard(mutex, &maple_keyb_mutex);
         |                                       ^
   In file included from include/linux/irqflags.h:17,
                    from arch/sh/include/asm/cmpxchg-irq.h:5,
                    from arch/sh/include/asm/cmpxchg.h:20,
                    from arch/sh/include/asm/atomic.h:19,
                    from include/linux/atomic.h:7,
                    from include/asm-generic/bitops/atomic.h:5,
                    from arch/sh/include/asm/bitops.h:23,
                    from include/linux/bitops.h:68,
                    from include/linux/kernel.h:23,
                    from drivers/input/keyboard/maple_keyb.c:9:
   include/linux/cleanup.h:166: note: macro "guard" defined here
     166 | #define guard(_name) \
         | 
>> drivers/input/keyboard/maple_keyb.c:211:9: error: 'guard' undeclared (first use in this function)
     211 |         guard(mutex, &maple_keyb_mutex);
         |         ^~~~~
   drivers/input/keyboard/maple_keyb.c:211:9: note: each undeclared identifier is reported only once for each function it appears in


vim +/guard +211 drivers/input/keyboard/maple_keyb.c

   205	
   206	static int remove_maple_kbd(struct device *dev)
   207	{
   208		struct maple_device *mdev = to_maple_dev(dev);
   209		struct dc_kbd *kbd = maple_get_drvdata(mdev);
   210	
 > 211		guard(mutex, &maple_keyb_mutex);
   212	
   213		input_unregister_device(kbd->dev);
   214		kfree(kbd);
   215	
   216		maple_set_drvdata(mdev, NULL);
   217		return 0;
   218	}
   219	

-- 
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki

Using guard notation makes the code more compact and error handling
more robust by ensuring that mutexes are released in all code paths
when control leaves critical section.

Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
---

v2: fix typo pointed out by the kernel test robot

 drivers/input/keyboard/maple_keyb.c |    9 ++-------
 1 file changed, 2 insertions(+), 7 deletions(-)

diff --git a/drivers/input/keyboard/maple_keyb.c b/drivers/input/keyboard/maple_keyb.c
index 91a1d2958109..1a8f1fa53fbb 100644
--- a/drivers/input/keyboard/maple_keyb.c
+++ b/drivers/input/keyboard/maple_keyb.c
@@ -132,14 +132,11 @@ static void dc_kbd_callback(struct mapleq *mq)
 	 * We should always get the lock because the only
 	 * time it may be locked is if the driver is in the cleanup phase.
 	 */
-	if (likely(mutex_trylock(&maple_keyb_mutex))) {
-
+	scoped_guard(mutex_try, &maple_keyb_mutex) {
 		if (buf[1] == mapledev->function) {
 			memcpy(kbd->new, buf + 2, 8);
 			dc_scan_kbd(kbd);
 		}
-
-		mutex_unlock(&maple_keyb_mutex);
 	}
 }
 
@@ -211,14 +208,12 @@ static int remove_maple_kbd(struct device *dev)
 	struct maple_device *mdev = to_maple_dev(dev);
 	struct dc_kbd *kbd = maple_get_drvdata(mdev);
 
-	mutex_lock(&maple_keyb_mutex);
+	guard(mutex)(&maple_keyb_mutex);
 
 	input_unregister_device(kbd->dev);
 	kfree(kbd);
 
 	maple_set_drvdata(mdev, NULL);
-
-	mutex_unlock(&maple_keyb_mutex);
 	return 0;
 }
 

-- 
Dmitry