Re: [PATCH v2] console: Add console=auto option
From: Petr Mladek <pmladek@suse.com>
Date: 2018-08-17 08:19:53
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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.
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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.
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If the device connected to the port is not a TTY but a braille device, prepend "brl," before the device type, for instancediff --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