linux-kernel - Re: [PATCH] acpi, spcr: Make SPCR available to x86

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Message-ID: <1e69fffc-1c3b-8cc0-f1cb-695de5ccdcb5@redhat.com>
Date:   Mon, 12 Feb 2018 08:47:57 -0500
From:   Prarit Bhargava <prarit@...hat.com>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     linux-kernel@...r.kernel.org, linux-acpi@...r.kernel.org,
        linux-doc@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-pm@...r.kernel.org, linux-serial@...r.kernel.org,
        Bhupesh Sharma <bhsharma@...hat.com>,
        Lv Zheng <lv.zheng@...el.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
        Jonathan Corbet <corbet@....net>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will.deacon@....com>,
        Timur Tabi <timur@...eaurora.org>, graeme.gregory@...aro.org,
        mark.salter@...hat.com
Subject: Re: [PATCH] acpi, spcr: Make SPCR available to x86



On 02/12/2018 08:34 AM, Peter Zijlstra wrote:
> On Thu, Jan 18, 2018 at 10:09:51AM -0500, Prarit Bhargava wrote:
>>  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.

>