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

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Date:   Sun, 9 Jul 2023 16:46:06 -0700
From:   Randy Dunlap <rdunlap@...radead.org>
To:     Raul E Rangel <rrangel@...omium.org>, linux-kernel@...r.kernel.org,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Petr Mladek <pmladek@...e.com>
Cc:     mario.limonciello@....com, kramasub@...omium.org,
        Alexander Potapenko <glider@...gle.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Ard Biesheuvel <ardb@...nel.org>,
        "Jason A. Donenfeld" <Jason@...c4.com>,
        Li Zhe <lizhe.67@...edance.com>,
        "Liam R. Howlett" <Liam.Howlett@...cle.com>,
        Mark Rutland <mark.rutland@....com>,
        Will Deacon <will@...nel.org>,
        Wolfram Sang <wsa+renesas@...g-engineering.com>,
        Zhou jie <zhoujie@...china.com>
Subject: Re: [PATCH] init: Don't proxy console= to earlycon



On 7/7/23 18:17, Raul E Rangel wrote:
> Right now we are proxying the `console=XXX` command line args to the
> param_setup_earlycon. This is done because the following are
> equivalent:
> 
>     console=uart[8250],mmio,<addr>[,options]
>     earlycon=uart[8250],mmio,<addr>[,options]
> 
> In addition, when `earlycon=` or just `earlycon` is specified on the
> command line, we look at the SPCR table or the DT to extract the device
> options.
> 
> When `console=` is specified on the command line, it's intention is to
> disable the console. Right now since we are proxying the `console=`

How do you figure this (its intention is to disable the console)?

> flag to the earlycon handler, we enable the earlycon_acpi_spcr_enable
> variable when an SPCR table is present. This means that we
> inadvertently enable the earlycon.
> 
> This change makes it so we only proxy the console= command if it's
> value is not empty. This way we can correctly handle both cases.
> 
> Signed-off-by: Raul E Rangel <rrangel@...omium.org>
> ---
> 
>  init/main.c | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
> 
> diff --git a/init/main.c b/init/main.c
> index aa21add5f7c54..f72bf644910c1 100644
> --- a/init/main.c
> +++ b/init/main.c
> @@ -738,8 +738,7 @@ static int __init do_early_param(char *param, char *val,
>  	for (p = __setup_start; p < __setup_end; p++) {
>  		if ((p->early && parameq(param, p->str)) ||
>  		    (strcmp(param, "console") == 0 &&
> -		     strcmp(p->str, "earlycon") == 0)
> -		) {
> +		     strcmp(p->str, "earlycon") == 0 && val && val[0])) {
>  			if (p->setup_func(val) != 0)
>  				pr_warn("Malformed early option '%s'\n", param);
>  		}

-- 
~Randy