This extends the "console=" interface to allow setting the per-console
loglevel by adding "/N" to the string, where N is the desired loglevel
expressed as a base 10 integer. Invalid values are silently ignored.

Cc: Petr Mladek <pmla...@suse.com>
Cc: Steven Rostedt <rost...@goodmis.org>
Cc: Sergey Senozhatsky <sergey.senozhat...@gmail.com>
Signed-off-by: Calvin Owens <calvinow...@fb.com>
---
 Documentation/admin-guide/kernel-parameters.txt |  6 ++---
 kernel/printk/console_cmdline.h                 |  1 +
 kernel/printk/printk.c                          | 30 ++++++++++++++++++++-----
 3 files changed, 28 insertions(+), 9 deletions(-)

diff --git a/Documentation/admin-guide/kernel-parameters.txt 
b/Documentation/admin-guide/kernel-parameters.txt
index 0549662..f22b992 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -607,10 +607,10 @@
                ttyS<n>[,options]
                ttyUSB0[,options]
                        Use the specified serial port.  The options are of
-                       the form "bbbbpnf", where "bbbb" is the baud rate,
+                       the form "bbbbpnf/l", where "bbbb" is the baud rate,
                        "p" is parity ("n", "o", or "e"), "n" is number of
-                       bits, and "f" is flow control ("r" for RTS or
-                       omit it).  Default is "9600n8".
+                       bits, "f" is flow control ("r" for RTS or omit it),
+                       and "l" is the loglevel on [0,7]. Default is "9600n8".
 
                        See Documentation/admin-guide/serial-console.rst for 
more
                        information.  See
diff --git a/kernel/printk/console_cmdline.h b/kernel/printk/console_cmdline.h
index 2ca4a8b..269e666 100644
--- a/kernel/printk/console_cmdline.h
+++ b/kernel/printk/console_cmdline.h
@@ -5,6 +5,7 @@ struct console_cmdline
 {
        char    name[16];                       /* Name of the driver       */
        int     index;                          /* Minor dev. to use        */
+       int     loglevel;                       /* Loglevel to use */
        char    *options;                       /* Options for the driver   */
 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
        char    *brl_options;                   /* Options for braille driver */
diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index 488bda3..4c14cf2 100644
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -1892,7 +1892,7 @@ asmlinkage __visible void early_printk(const char *fmt, 
...)
 #endif
 
 static int __add_preferred_console(char *name, int idx, char *options,
-                                  char *brl_options)
+                                  int loglevel, char *brl_options)
 {
        struct console_cmdline *c;
        int i;
@@ -1918,6 +1918,7 @@ static int __add_preferred_console(char *name, int idx, 
char *options,
        c->options = options;
        braille_set_options(c, brl_options);
 
+       c->loglevel = loglevel;
        c->index = idx;
        return 0;
 }
@@ -1928,8 +1929,8 @@ static int __add_preferred_console(char *name, int idx, 
char *options,
 static int __init console_setup(char *str)
 {
        char buf[sizeof(console_cmdline[0].name) + 4]; /* 4 for "ttyS" */
-       char *s, *options, *brl_options = NULL;
-       int idx;
+       char *s, *options, *llevel, *brl_options = NULL;
+       int idx, loglevel = LOGLEVEL_EMERG;
 
        if (_braille_console_setup(&str, &brl_options))
                return 1;
@@ -1947,6 +1948,14 @@ static int __init console_setup(char *str)
        options = strchr(str, ',');
        if (options)
                *(options++) = 0;
+
+       llevel = strchr(str, '/');
+       if (llevel) {
+               *(llevel++) = 0;
+               if (kstrtoint(llevel, 10, &loglevel))
+                       loglevel = LOGLEVEL_EMERG;
+       }
+
 #ifdef __sparc__
        if (!strcmp(str, "ttya"))
                strcpy(buf, "ttyS0");
@@ -1959,7 +1968,7 @@ static int __init console_setup(char *str)
        idx = simple_strtoul(s, NULL, 10);
        *s = 0;
 
-       __add_preferred_console(buf, idx, options, brl_options);
+       __add_preferred_console(buf, idx, options, loglevel, brl_options);
        console_set_on_cmdline = 1;
        return 1;
 }
@@ -1980,7 +1989,8 @@ __setup("console=", console_setup);
  */
 int add_preferred_console(char *name, int idx, char *options)
 {
-       return __add_preferred_console(name, idx, options, NULL);
+       return __add_preferred_console(name, idx, options, LOGLEVEL_EMERG,
+                                      NULL);
 }
 
 bool console_suspend_enabled = true;
@@ -2475,6 +2485,7 @@ void register_console(struct console *newcon)
        struct console *bcon = NULL;
        struct console_cmdline *c;
        static bool has_preferred;
+       bool extant = false;
 
        if (console_drivers)
                for_each_console(bcon)
@@ -2541,6 +2552,12 @@ void register_console(struct console *newcon)
                        if (newcon->index < 0)
                                newcon->index = c->index;
 
+                       /*
+                        * Carry over the loglevel from the cmdline
+                        */
+                       newcon->level = c->loglevel;
+                       extant = true;
+
                        if (_braille_register_console(newcon, c))
                                return;
 
@@ -2572,8 +2589,9 @@ void register_console(struct console *newcon)
        /*
         * By default, the per-console minimum forces no messages through.
         */
-       newcon->level = LOGLEVEL_EMERG;
        newcon->kobj = NULL;
+       if (!extant)
+               newcon->level = LOGLEVEL_EMERG;
 
        /*
         *      Put this console in the list - keep the
-- 
2.9.5

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