Re: [PATCH] init: Don't proxy console= to earlycon

[Raul Rangel]

On Wed, Aug 21, 2024 at 8:38 AM Petr Mladek <pmladek@xxxxxxxx> wrote:
>
> On Thu 2024-08-08 11:30:53, Raul Rangel wrote:
> > On Fri, Jul 28, 2023 at 11:57 AM Raul Rangel <rrangel@xxxxxxxxxxxx> wrote:
> > > > Your patch is good then. Well, would you mind to add a comment into
> > > > the code and make the commit message more clear even for dummies like
> > > > me?
> > > >
> > > > Something like the patch below. It would be better to split it into
> > > > two:
> > > >
> > > >    + 1st shuffling the check and adding the first part of the comment
> > > >    + 2nd fixing the case with empty console= options.
> > > >
> > > > I could prepare the patchset. I would keep your SOB for the 2nd patch
> > > > if you agreed.
> > >
> > > Yes, feel free. Thanks!
> > >
> >
> > Hey Petr,
> > I was just following up on this. Were you going to prepare the two patches?
>
> I have been quite overloaded last two years. It would help me a lot if
> you could prepare the two patches and send them for review.
>
> Thanks for re-opening this. It has already fallen through cracks on my
> side /o\.
>
> Best Regards,
> Petr

No worries, we were just going through our tech debt backlog and this
patch came up.

Thinking about this a little bit more, I'm wondering if we can clean
up the hack. Would something like the following patch work? My thought
is we declare an early handler for `console=`, so we can handle the
`console=uartXXXX` case, and leave the non-early handler in place to
handle the `console=ttyXX` cases.

diff --git a/drivers/tty/serial/earlycon.c b/drivers/tty/serial/earlycon.c
index a5f380584cdae7..7a48fe6fc0dffc 100644
--- a/drivers/tty/serial/earlycon.c
+++ b/drivers/tty/serial/earlycon.c
@@ -241,6 +241,21 @@ static int __init param_setup_earlycon(char *buf)
 }
 early_param("earlycon", param_setup_earlycon);

+static int __init param_setup_earlycon_console_alias(char *buf)
+{
+       /* We only want to handle `console=XXXX` in this handler. We leave
+          `console` and `console=` to be handled later by the non-early printk
+          handler.
+       */
+       if (!buf || !buf[0]) {
+               return 0;
+       }
+
+       /* `console=uartXXXX` is actually an alias for `earlycon=uartXXXX`. */
+       return param_setup_earlycon(buf);
+}
+early_param("console=", param_setup_earlycon_console_alias);
+
 #ifdef CONFIG_OF_EARLY_FLATTREE

 int __init of_setup_earlycon(const struct earlycon_id *match,
diff --git a/init/main.c b/init/main.c
index 8e1f6127e172c3..b6f0cb424176da 100644
--- a/init/main.c
+++ b/init/main.c
@@ -740,9 +740,7 @@ static int __init do_early_param(char *param, char *val,
        const struct obs_kernel_param *p;

        for (p = __setup_start; p < __setup_end; p++) {
-               if ((p->early && parameq(param, p->str)) ||
-                   (strcmp(param, "console") == 0 &&
-                    strcmp(p->str, "earlycon") == 0 && val && val[0])) {
+               if ((p->early && parameq(param, p->str))) {
                        if (p->setup_func(val) != 0)
                                pr_warn("Malformed early option '%s'\n", param);
                }


>
>
> > > > Here is the proposal:
> > > >
> > > > From d2fb7c54bed4c67df229c56fcc1b0af83ada5227 Mon Sep 17 00:00:00 2001
> > > > From: Raul E Rangel <rrangel@xxxxxxxxxxxx>
> > > > Date: Fri, 7 Jul 2023 19:17:25 -0600
> > > > Subject: [PATCH] init: Don't proxy the empty console= options to earlycon
> > > >
> > > > Right now we are proxying the `console=XXX` command line args to the
> > > > param_setup_earlycon. This is done because the early consoles used to
> > > > be enabled via the `console` parameter.
> > > >
> > > > The `earlycon` parameter was added later by the commit 18a8bd949d6adb311
> > > > ("serial: convert early_uart to earlycon for 8250"). It allowed to
> > > > setup the early consoles using another callback. And it was indeed
> > > > more self-explanatory and cleaner approach.
> > > >
> > > > As a result, for example, the following parameters have the same effect:
> > > >
> > > >     console=uart[8250],mmio,<addr>[,options]
> > > >     earlycon=uart[8250],mmio,<addr>[,options]
> > > >
> > > > Nevertheless, `console` and `earlycon` parameters behave different when
> > > > the options do not match an early console. setup_earlycon() accepts only
> > > > console names in __earlycon_table. Also the empty options are handled
> > > > differently:
> > > >
> > > >   + When `earlycon=` or just `earlycon` is specified on the command line,
> > > >     param_setup_earlycon() tries to enable an early console via the SPCR
> > > >     table or the device tree.
> > > >
> > > >   + When `console=` is specified on the command line, it's intention is to
> > > >     disable the console.
> > > >
> > > > Here comes the problem. The current code calls param_setup_earlycon()
> > > > even when `console=` is used with no options. As a result, it might
> > > > enable the early console when it is defined in the SPCR table or
> > > > a device tree. This is obviously not what users want.
> > > >
> > > > The early console should be enabled via SPCR or DT only when `earlycon`
> > > > is used explicitly with no options.
> > > >
> > > > Signed-off-by: Raul E Rangel <rrangel@xxxxxxxxxxxx>
> > > > [pmladek@xxxxxxxx: Add comments and more details into the commit message]
> > > > ---
> > > >  init/main.c | 20 ++++++++++++++++----
> > > >  1 file changed, 16 insertions(+), 4 deletions(-)
> > > >
> > > > diff --git a/init/main.c b/init/main.c
> > > > index ad920fac325c..3b059e316e62 100644
> > > > --- a/init/main.c
> > > > +++ b/init/main.c
> > > > @@ -733,13 +733,25 @@ static int __init do_early_param(char *param, char *val,
> > > >         const struct obs_kernel_param *p;
> > > >
> > > >         for (p = __setup_start; p < __setup_end; p++) {
> > > > -               if ((p->early && parameq(param, p->str)) ||
> > > > -                   (strcmp(param, "console") == 0 &&
> > > > -                    strcmp(p->str, "earlycon") == 0)
> > > > -               ) {
> > > > +               if (p->early && parameq(param, p->str)) {
> > > >                         if (p->setup_func(val) != 0)
> > > >                                 pr_warn("Malformed early option '%s'\n", param);
> > > >                 }
> > > > +
> > > > +               /*
> > > > +                * Early consoles can be historically enabled also when earlycon
> > > > +                * specific options are passed via console=[earlycon options]
> > > > +                * parameter.
> > > > +                *
> > > > +                * Do not try it with an empty value. "console=" is used to
> > > > +                * disable real normal consoles. While "earlycon" is used to
> > > > +                * enable an early console via SPCR or DT.
> > > > +                */
> > > > +               if (strcmp(param, "console") == 0 && val && val[0] &&
> > > > +                   strcmp(p->str, "earlycon") == 0) {
> > > > +                       if (p->setup_func(val) != 0)
> > > > +                               pr_warn("Failed to setup earlycon via console=%s\n", val);
> > > > +               }
> > > >         }
> > > >         /* We accept everything at this stage. */
> > > >         return 0;
> > > > --
> > > > 2.35.3
> > > >
> > >
> > > Signed-off-by: Raul E Rangel <rrangel@xxxxxxxxxxxx>
> >
> > Thanks,
> > Raul