serial: core: Handle serial console options

In order to start moving the serial console quirks out of console_setup(),
let's add parsing for the quirks to the serial core layer. We can use
serial_base_add_one_prefcon() to handle the quirks.

Note that eventually we may want to set up driver specific console quirk
handling for the serial port device drivers to use. But we need to figure
out which driver(s) need to call the quirk. So for now, we just handle the
sparc quirk directly.

Signed-off-by: Tony Lindgren <tony@atomide.com>
Link: https://lore.kernel.org/r/20240327110021.59793-6-tony@atomide.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/serial/serial_base_bus.c

@@ -219,9 +219,58 @@ static int serial_base_add_one_prefcon(const char *match, const char *dev_name,
 	return ret;
 }
 
+#ifdef __sparc__
+
+/* Handle Sparc ttya and ttyb options as done in console_setup() */
+static int serial_base_add_sparc_console(const char *dev_name, int idx)
+{
+	const char *name;
+
+	switch (idx) {
+	case 0:
+		name = "ttya";
+		break;
+	case 1:
+		name = "ttyb";
+		break;
+	default:
+		return 0;
+	}
+
+	return serial_base_add_one_prefcon(name, dev_name, idx);
+}
+
+#else
+
+static inline int serial_base_add_sparc_console(const char *dev_name, int idx)
+{
+	return 0;
+}
+
+#endif
+
 static int serial_base_add_prefcon(const char *name, int idx)
 {
 	const char *char_match __free(kfree) = NULL;
+	const char *nmbr_match __free(kfree) = NULL;
+	int ret;
+
+	/* Handle ttyS specific options */
+	if (strstarts(name, "ttyS")) {
+		/* No name, just a number */
+		nmbr_match = kasprintf(GFP_KERNEL, "%i", idx);
+		if (!nmbr_match)
+			return -ENODEV;
+
+		ret = serial_base_add_one_prefcon(nmbr_match, name, idx);
+		if (ret)
+			return ret;
+
+		/* Sparc ttya and ttyb */
+		ret = serial_base_add_sparc_console(name, idx);
+		if (ret)
+			return ret;
+	}
 
 	/* Handle the traditional character device name style console=ttyS0 */
 	char_match = kasprintf(GFP_KERNEL, "%s%i", name, idx);