Re: [PATCH v5 09/16] printk: Allow to override options via the command line

[John Ogness <john.ogness@linutronix.de>]

On 2026-10-29, Chris Down <chris@chrisdown.name> wrote:
>>Consoles can be preferred either via the console= command line parameter
>>or by some platform specific code, e.g. SPCR, device tree.
>
> On v4 I recall you said you would probably do the change in a separate series. 
> I think that is still the better plan: the rest of the series is a clean-up and 
> it would be nice to keep it that way.
>
>>-	 * Historically, the preferred options are stored only by the first
>>-	 * caller who prefers the particular console.
>>+	 * Allow to override options via the command line but always
>>+	 * prefer the Braille variant.
>> 	 */
>>-	if (is_new_entry) {
>>+	if (is_new_entry || brl_options ||
>>+	    (user_specified && !is_braille_console_preferred(pc))) {
>
> This also clears options when the later console= has none, which v4 did not do. 
> That breaks at least the MIPS boards that pass the firmware baud rate from 
> setup_arch():
>
>     arch/mips/sgi-ip22/ip22-setup.c: add_preferred_console("ttyS", n, dbaud)
>     arch/mips/sgi-ip32/ip32-setup.c: add_preferred_console("ttyS", n, dbaud)
>     arch/mips/sni/setup.c:           add_preferred_console("ttyS"/"ttySC", port, baud)
>
> With "console=ttyS0" and no options, the drivers there (ip22zilog, 8250, 
> sccnxp) fall back to 9600, and anyone with the firmware set to another rate is 
> gonna have a bad time.
>
> It also makes a bare "console=uart" after an SPCR "uart" entry oops because 
> univ8250_console_match() hands the now-NULL options to uart_parse_earlycon().
>
> (A bare console=uart on its own already oopses in the base, so that part is an 
> older 8250 problem, but this patch adds a fun new way to get there.)
>
> If you want to keep it here, could it at least only override when the command 
> line actually provides options?

Agreed. It should be (user_specified && options && ...)

A console specified with no options should not be interpretted as "clear
options" but rather "not overriding options, just specifying that it is
preferred".

John