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Subject[PATCH 3/3] printk: Add ability to set loglevel via "console=" cmdline
Date
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 <pmladek@suse.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Signed-off-by: Calvin Owens <calvinowens@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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