[PATCH v3 09/11] printk: Handle pre-enabled consoles in the top-level try_enable_console()

[Petr Mladek]

The function try_enable_preferred_console() currently has the
non-obvious side effect of returning success for consoles that are
already pre-enabled. This obscures the logic flow during console
registration.

Move the check for pre-enabled consoles directly into the top-level
try_enable_console(). This change makes the handling of pre-enabled
consoles explicit and easier to follow.

Furthermore, this separation lays the groundwork for future cleanups
where try_enable_preferred_console() can be restricted to cases where
an entry actually exists in the preferred_consoles[] array.

Possible behavior change:

try_enable_preferred_console() will newly be called also with
@user_specified parameter set to "false" when it failed with the "true"
variant. But it looks like the right way to do. It will allow to call
newcon->setup() when the console was preferred by some platform
specific code.

Signed-off-by: Petr Mladek <pmladek@xxxxxxxx>
---
 kernel/printk/printk.c | 25 +++++++++++++------------
 1 file changed, 13 insertions(+), 12 deletions(-)

diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index 97327c27436a..a4eaf157cece 100644
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -3993,9 +3993,6 @@ static int console_call_setup(struct console *newcon, char *options)
  * the newly registered console with any of the ones selected
  * by either the command line or add_preferred_console() and
  * setup/enable it.
- *
- * Care need to be taken with consoles that are statically
- * enabled such as netconsole
  */
 static int __try_enable_preferred_console(struct console *newcon,
 					  bool user_specified,
@@ -4048,14 +4045,6 @@ static int __try_enable_preferred_console(struct console *newcon,
 		return 0;
 	}
 
-	/*
-	 * Some consoles, such as pstore and netconsole, can be enabled even
-	 * without matching. Accept the pre-enabled consoles only when match()
-	 * and setup() had a chance to be called.
-	 */
-	if (newcon->flags & CON_ENABLED && pc->user_specified == user_specified)
-		return 0;
-
 	return -ENOENT;
 }
 
@@ -4135,7 +4124,19 @@ static int try_enable_console(struct console *newcon)
 		return err;
 
 	/* If not, try to match against the platform default(s) */
-	return try_enable_preferred_console(newcon, false);
+	err = try_enable_preferred_console(newcon, false);
+	if (err != -ENOENT)
+		return err;
+
+	/*
+	 * Some consoles, such as pstore and netconsole, can be enabled even
+	 * without matching. Accept them at this stage when they had a chance
+	 * to match() and call setup().
+	 */
+	if (newcon->flags & CON_ENABLED)
+		err = 0;
+
+	return err;
 }
 
 /* Return the starting sequence number for a newly registered console. */
-- 
2.54.0