linux-kernel - Re: ARC no console output (was Re: [PATCH 1/2] init/console: Use ttynull as a fallback when there is no console)

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Message-ID: <87turkfq32.fsf@dell.be.48ers.dk>
Date:   Wed, 13 Jan 2021 23:07:45 +0100
From:   Peter Korsgaard <peter@...sgaard.com>
To:     Vineet Gupta <vgupta@...opsys.com>
Cc:     Petr Mladek <pmladek@...e.com>, linux-arch@...r.kernel.org,
        Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>,
        John Ogness <john.ogness@...utronix.de>,
        Shreyas Joshi <shreyas.joshi@...mp.com>,
        linux-kernel@...r.kernel.org, Steven Rostedt <rostedt@...dmis.org>,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
        Thomas Petazzoni <thomas.petazzoni@...tlin.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        buildroot@...ybox.net, arcml <linux-snps-arc@...ts.infradead.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        shreyasjoshi15@...il.com, Guenter Roeck <linux@...ck-us.net>
Subject: Re: ARC no console output (was Re: [PATCH 1/2] init/console: Use ttynull as a fallback when there is no console)

>>>>> "Vineet" == Vineet Gupta <vgupta@...opsys.com> writes:

 > On 1/7/21 9:04 AM, Petr Mladek wrote:
 >> On Thu 2021-01-07 08:43:16, Vineet Gupta wrote:
 >>> Hi John,
 >>> 
 >>> On 1/7/21 1:02 AM, John Ogness wrote:
 >>>> Hi Vineet,
 >>>> 
 >>>> On 2021-01-06, Vineet Gupta <vgupta@...opsys.com> wrote:
 >>>>> This breaks ARC booting (no output on console).
 >>>> 
 >>>> Could you provide the kernel boot arguments that you use? This series is
 >>>> partly about addressing users that have used boot arguments that are
 >>>> technically incorrect (even if had worked). Seeing the boot arguments of
 >>>> users that are not experiencing problems may help to reveal some of the
 >>>> unusual console usages until now.
 >>> 
 >>> 
 >>> Kernel command line: earlycon=uart8250,mmio32,0xf0005000,115200n8
 >>> console=ttyS0,115200n8 debug print-fatal-signals=1
 >> 
 >> This is strange, the problematic patch should use ttynull
 >> only as a fallback. It should not be used when a particular console
 >> is defined on the command line.

 > What happens in my case is console_on_rootfs() doesn't find
 > /dev/console and switching to ttynull. /dev is not present because
 > devtmpfs doesn't automount for initramfs.

But our initramfs/cpio logic ensures that the initramfs has a static
/dev/console device node, so how can that be?

https://git.buildroot.net/buildroot/tree/fs/cpio/cpio.mk#n25

-- 
Bye, Peter Korsgaard