linux-kernel - [PATCH v5 5/7] console: Avoid positive return code from unregister

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Message-Id: <20200203133130.11591-5-andriy.shevchenko@linux.intel.com>
Date:   Mon,  3 Feb 2020 15:31:28 +0200
From:   Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:     Petr Mladek <pmladek@...e.com>,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
        linux-kernel@...r.kernel.org, Steven Rostedt <rostedt@...dmis.org>
Cc:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Subject: [PATCH v5 5/7] console: Avoid positive return code from unregister_console()

There are only two callers that use the returned code from
unregister_console():

  - unregister_early_console() in arch/m68k/kernel/early_printk.c
  - kgdb_unregister_nmi_console() in drivers/tty/serial/kgdb_nmi.c

They both expect to get "0" on success and a non-zero value on error.
But the current behavior is confusing and buggy:

  - _braille_unregister_console() returns "1" on success
  - unregister_console() returns "1" on error

Fix and clean up the behavior:

  - Return success when _braille_unregister_console() succeeded
  - Return a meaningful error code when the console was not registered before

Signed-off-by: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
---
v5: no change

 kernel/printk/printk.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index 463ed5c5474e..5fdae891a4cd 100644
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -2823,10 +2823,12 @@ int unregister_console(struct console *console)
 		console->name, console->index);
 
 	res = _braille_unregister_console(console);
-	if (res)
+	if (res < 0)
 		return res;
+	if (res > 0)
+		return 0;
 
-	res = 1;
+	res = -ENODEV;
 	console_lock();
 	if (console_drivers == console) {
 		console_drivers=console->next;
-- 
2.24.1