Messages in this thread | | | Date | Fri, 17 Aug 2018 10:19:47 +0200 | From | Petr Mladek <> | Subject | Re: [PATCH v2] console: Add console=auto option |
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On Thu 2018-08-16 13:39:01, Prarit Bhargava wrote: > ACPI may contain an SPCR table that defines a default system console. > On ARM if the table is present then the SPCR console is enabled by default. > On x86 the SPCR console is used if 'earlycon' (no parameters) is > specified as a kernel parameter and is used only as the early console. > To use the SPCR data as a console a user must boot with 'earlycon', > grep logs & specify a console= kernel parameter, and then reboot again. > > Add 'console=auto' that enables a firmware or hardware console, and on > x86 enable the SPCR console if 'console=auto' is specified.
I basically like the idea. Just one or two nits below.
> diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt > index a32f2a126791..dd057224f33b 100644 > --- a/Documentation/admin-guide/kernel-parameters.txt > +++ b/Documentation/admin-guide/kernel-parameters.txt > @@ -635,6 +635,7 @@ > > hvc<n> Use the hypervisor console device <n>. This is for > both Xen and PowerPC hypervisors. > + auto [X86] Enable ACPI SPCR console
The "auto" option sounds reasonable. But earlycon does exactly this when used without no extra options. I prefer to stay consistent with the existing earlycon behavior.
> If the device connected to the port is not a TTY but a braille > device, prepend "brl," before the device type, for instance > diff --git a/arch/x86/kernel/acpi/boot.c b/arch/x86/kernel/acpi/boot.c > index 3b20607d581b..fb2616ba3b21 100644 > --- a/arch/x86/kernel/acpi/boot.c > +++ b/arch/x86/kernel/acpi/boot.c > @@ -1771,3 +1771,8 @@ void __init arch_reserve_mem_area(acpi_physical_address addr, size_t size) > e820__range_add(addr, size, E820_TYPE_ACPI); > e820__update_table_print(); > } > + > +void __init arch_console_setup(void) > +{ > + acpi_parse_spcr(false, true);
Just for record. I was curious that this might be called twice (also from acpi_boot_init(). But it looks safe after all.
The trick is in the two bool parameters. One call allows to register/enable earlycon and ignores normal console. This other call does exactly the opposite. I do not see any unwanted side effects.
Best Regards, Petr
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