Messages in this thread Patch in this message | | | Date | Fri, 3 Nov 2017 16:15:53 +0100 | From | Petr Mladek <> | Subject | Re: [PATCH 3/3] printk: Add ability to set loglevel via "console=" cmdline |
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On Thu 2017-09-28 17:43:57, Calvin Owens wrote: > 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". >
If I get this correctly, the patch allows to define the loglevel for any console. I think that we need to describe it in a generic way. Something like:
console= [KNL] Output console device and options.
Format: name[,options][/min_loglevel]
Where "name" is the console name, "options" are console-specific options, and "min_loglevel" allows to increase the loglevel for a particular console over the global one.
tty<n> Use the virtual console device <n>.
I would also add a cross reference into the loglevel= section about that the global loglevel might be overridden by a higher console-specific min_loglevel value.
> 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 */
Again, I would use "min_loglevel".
> 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 > @@ -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;
I would personally do the following:
if (!newcon->min_loglevel) newcon->min_loglevel = c->min_loglevel;
It is similar to newcon->index handling above. It will use the command line setting only when the console is registered for the first time.
All this is based on my assumption that all non-initialized struct console members are zero. At least I do not see any location where some other members would be explicitly zeroed. And there might be candidates, e.g. data, match(), next.
In each case, I do not know what the shortcut "extant" stands for and I feel confused ;-)
> 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;
I believe that this is not necessary.
Otherwise, I really like this approach. I am surprised that all consoles might be supported so easily.
Well, I am not 100% sure that '/' delimiter is the best choice. I hope that it will not cause any confusion. But I cannot think of anything better.
Best Regards, Petr
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