[PATCH 3/8] printk: Separate code for adding/updating preferred console metadata

[Petr Mladek <pmladek@suse.com>]

The logic for adding or updating a preferred console is currently
duplicated within __add_preferred_console(), making the code difficult
to follow and prone to consistency issues.

Introduce update_preferred_console() to centralize the initialization
and updating of struct preferred_console entries. This refactoring
explicitly defines and enforces the following rules:

1. Console names and/or indexes are not set when a console is preferred
   via devname; these are resolved later during device matching.
2. Console names are only added alongside a valid index.
3. Only matching entries are updated.
4. Console and Braille options are never cleared. They are updated
   only via the command line.
5. The global 'preferred_dev_console' index and 'console_set_on_cmdline'
   flag are updated consistently.

Additionally, rename braille_set_options() to braille_update_options()
to better reflect its conditional behavior.

While this is primarily a refactoring, it fixes two minor behavioral
consistencies: console options can now be overridden via the command
line, and Braille options are preserved even if a non-Braille console
with the same name was previously defined.

Signed-off-by: Petr Mladek <pmladek@suse.com>
---
 kernel/printk/braille.h |   7 +--
 kernel/printk/printk.c  | 110 +++++++++++++++++++++++++++-------------
 2 files changed, 80 insertions(+), 37 deletions(-)

diff --git a/kernel/printk/braille.h b/kernel/printk/braille.h
index 55cd3178a17a..0bdac303f8b1 100644
--- a/kernel/printk/braille.h
+++ b/kernel/printk/braille.h
@@ -5,9 +5,10 @@
 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
 
 static inline void
-braille_set_options(struct preferred_console *pc, char *brl_options)
+braille_update_options(struct preferred_console *pc, char *brl_options)
 {
-	pc->brl_options = brl_options;
+	if (brl_options)
+		pc->brl_options = brl_options;
 }
 
 /*
@@ -29,7 +30,7 @@ _braille_unregister_console(struct console *console);
 #else
 
 static inline void
-braille_set_options(struct preferred_console *pc, char *brl_options)
+braille_update_options(struct preferred_console *pc, char *brl_options)
 {
 }
 
diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index 3f856a438e74..ee57c7ac9d02 100644
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -2491,18 +2491,82 @@ asmlinkage __visible void early_printk(const char *fmt, ...)
 }
 #endif
 
-static void set_user_specified(struct preferred_console *pc, bool user_specified)
+static int update_preferred_console(int i, const char *name, const short idx,
+				    const char *devname, char *options,
+				    char *brl_options, bool user_specified)
 {
-	if (!user_specified)
-		return;
+	struct preferred_console *pc;
+
+	if (i >= MAX_PREFERRED_CONSOLES)
+		return -E2BIG;
+
+	pc = &preferred_consoles[i];
+
+	if (!name && !devname)
+		return -EINVAL;
+
+	if (devname) {
+		/*
+		 * A valid console name and index will get assigned when
+		 * a matching device gets registered.
+		 */
+		if (name) {
+			pr_err("Adding a preferred console devname with a hard-coded console name: %s, %s\n",
+			       devname, name);
+			return -EINVAL;
+		}
+		if (idx != -1) {
+			pr_err("Adding a preferred console devname with a hard-coded index: %s, %d\n",
+			       devname, idx);
+			return -EINVAL;
+		}
+
+		if (!pc->devname[0]) {
+			strscpy(pc->devname, devname);
+			pc->index = idx;
+		} else if (strcmp(pc->devname, devname) != 0) {
+			pr_err("Updating a preferred console with an invalid devname: %s vs. %s\n",
+			       pc->devname, devname);
+			return -EINVAL;
+		}
+	}
+
+	if (name) {
+		/* A console name must be defined with a valid index. */
+		if (idx < 0) {
+			pr_err("Adding a preferred console with an invalid index: %s, %d\n",
+			       name, idx);
+			return -EINVAL;
+		}
+
+		if (!pc->name[0]) {
+			strscpy(pc->name, name);
+			pc->index = idx;
+		} else if (strcmp(pc->name, name) != 0 || pc->index != idx) {
+			pr_err("Updating a preferred console with an invalid name or index: %s%d vs. %s%d\n",
+			       pc->name, pc->index, name, idx);
+			return -EINVAL;
+		}
+	}
+
+	if (!pc->options || (user_specified && options))
+		pc->options = options;
+
+	braille_update_options(pc, brl_options);
+
+	if (!brl_options)
+		preferred_dev_console = i;
 
 	/*
 	 * @c console was defined by the user on the command line.
 	 * Do not clear when added twice also by SPCR or the device tree.
 	 */
-	pc->user_specified = true;
-	/* At least one console defined by the user on the command line. */
-	console_set_on_cmdline = 1;
+	if (user_specified) {
+		pc->user_specified = true;
+		console_set_on_cmdline = 1;
+	}
+
+	return 0;
 }
 
 static int __add_preferred_console(const char *name, const short idx,
@@ -2515,14 +2579,6 @@ static int __add_preferred_console(const char *name, const short idx,
 	if (!name && !devname)
 		return -EINVAL;
 
-	/*
-	 * We use a signed short index for struct console for device drivers to
-	 * indicate a not yet assigned index or port. However, a negative index
-	 * value is not valid when the console name and index are defined on
-	 * the command line.
-	 */
-	if (name && idx < 0)
-		return -EINVAL;
 
 	/*
 	 *	See if this tty is not yet registered, and
@@ -2531,28 +2587,14 @@ static int __add_preferred_console(const char *name, const short idx,
 	for (i = 0, pc = preferred_consoles;
 	     i < MAX_PREFERRED_CONSOLES && (pc->name[0] || pc->devname[0]);
 	     i++, pc++) {
-		if ((name && strcmp(pc->name, name) == 0 && pc->index == idx) ||
-		    (devname && strcmp(pc->devname, devname) == 0)) {
-			if (!brl_options)
-				preferred_dev_console = i;
-			set_user_specified(pc, user_specified);
-			return 0;
-		}
+		if (name && strcmp(pc->name, name) == 0 && pc->index == idx)
+			break;
+		if (devname && strcmp(pc->devname, devname) == 0)
+			break;
 	}
-	if (i == MAX_PREFERRED_CONSOLES)
-		return -E2BIG;
-	if (!brl_options)
-		preferred_dev_console = i;
-	if (name)
-		strscpy(pc->name, name);
-	if (devname)
-		strscpy(pc->devname, devname);
-	pc->options = options;
-	set_user_specified(pc, user_specified);
-	braille_set_options(pc, brl_options);
 
-	pc->index = idx;
-	return 0;
+	return update_preferred_console(i, name, idx, devname, options,
+					brl_options, user_specified);
 }
 
 static int __init console_msg_format_setup(char *str)
-- 
2.52.0