linux-kernel - Re: [RFC PATCH 0/3] drm/log: Introduce a new boot logger to draw the kmsg on the screen

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Message-ID: <87r0b8zg0u.fsf@jogness.linutronix.de>
Date: Thu, 01 Aug 2024 12:42:17 +0206
From: John Ogness <john.ogness@...utronix.de>
To: Jocelyn Falempe <jfalempe@...hat.com>, Maarten Lankhorst
 <maarten.lankhorst@...ux.intel.com>, Maxime Ripard <mripard@...nel.org>,
 Thomas Zimmermann <tzimmermann@...e.de>, David Airlie <airlied@...il.com>,
 Daniel Vetter <daniel@...ll.ch>, Javier Martinez Canillas
 <javierm@...hat.com>, "Guilherme G . Piccoli" <gpiccoli@...lia.com>,
 bluescreen_avenger@...izon.net, dri-devel@...ts.freedesktop.org,
 linux-kernel@...r.kernel.org
Cc: Jocelyn Falempe <jfalempe@...hat.com>
Subject: Re: [RFC PATCH 0/3] drm/log: Introduce a new boot logger to draw
 the kmsg on the screen

On 2024-08-01, Jocelyn Falempe <jfalempe@...hat.com> wrote:
>  * I tried to use the new nbcon interface, but didn't get any message
>  from the write_atomic() callback, but the goal is to use that when
>  it's ready.

Be aware that the write_atomic() callback _must_ also print from NMI
context. write_thread() may be the callback you are interested
instead. Note that for CON_NBCON, write_atomic() is optional,
write_thread() is mandatory.

Disclaimer: All of this currently only available in the PREEMPT_RT
patchset. So until it hits mainline, semantics may yet change.

John Ogness