printk: Save console options for add_preferred_console_match()

Driver subsystems may need to translate the preferred console name to the
character device name used. We already do some of this in console_setup()
with a few hardcoded names, but that does not scale well.

The console options are parsed early in console_setup(), and the consoles
are added with __add_preferred_console(). At this point we don't know much
about the character device names and device drivers getting probed.

To allow driver subsystems to set up a preferred console, let's save the
kernel command line console options. To add a preferred console from a
driver subsystem with optional character device name translation, let's
add a new function add_preferred_console_match().

This allows the serial core layer to support console=DEVNAME:0.0 style
hardware based addressing in addition to the current console=ttyS0 style
naming. And we can start moving console_setup() character device parsing
to the driver subsystem specific code.

We use a separate array from the console_cmdline array as the character
device name and index may be unknown at the console_setup() time. And
eventually there's no need to call __add_preferred_console() until the
subsystem is ready to handle the console.

Adding the console name in addition to the character device name, and a
flag for an added console, could be added to the struct console_cmdline.
And the console_cmdline array handling could be modified accordingly. But
that complicates things compared saving the console options, and then
adding the consoles when the subsystems handling the consoles are ready.

Co-developed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/r/20240327110021.59793-2-tony@atomide.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 11 insertions, 3 deletions

diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index adf99c05adca..05919491c5a2 100644
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -383,9 +383,6 @@ static int console_locked;
 /*
  *	Array of consoles built from command line options (console=)
  */
-
-#define MAX_CMDLINECONSOLES 8
-
 static struct console_cmdline console_cmdline[MAX_CMDLINECONSOLES];
 
 static int preferred_console = -1;
@@ -2503,6 +2500,10 @@ static int __init console_setup(char *str)
 	if (_braille_console_setup(&str, &brl_options))
 		return 1;
 
+	/* Save the console for driver subsystem use */
+	if (console_opt_save(str, brl_options))
+		return 1;
+
 	/*
 	 * Decode str into name, index, options.
 	 */
@@ -2533,6 +2534,13 @@ static int __init console_setup(char *str)
 }
 __setup("console=", console_setup);
 
+/* Only called from add_preferred_console_match() */
+int console_opt_add_preferred_console(const char *name, const short idx,
+				      char *options, char *brl_options)
+{
+	return __add_preferred_console(name, idx, options, brl_options, true);
+}
+
 /**
  * add_preferred_console - add a device to the list of preferred consoles.
  * @name: device name