On 02/12/2018 08:34 AM, Peter Zijlstra wrote:

On Thu, Jan 18, 2018 at 10:09:51AM -0500, Prarit Bhargava wrote:

quoted

 config ACPI_SPCR_TABLE
+	bool "ACPI Serial Port Console Redirection Support"
+	default y if X86
+	help
+	  Enable support for Serial Port Console Redirection (SPCR) Table.
+	  This table provides information about the configuration of the
+	  earlycon console.

I just got asked this by oldconfig, which left me rather puzzled, WTF
does this do?

Odd -- I thought I had taken care of that :(  My apologies Peter.

ACPI SPCR is used by a vendor to define the serial console for a system.  If
SPCR exists a user can add kernel parameter "earlycon" (no extra kernel
parameters) and the console will work out-of-the-box.

The serial console configuration varies from vendor to vendor.  This takes the
guess-work out of defining a serial console.

P.