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 <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".
>
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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