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Message-ID: <782f6c32-73ed-4e58-ae10-ff2d486b499c@linaro.org>
Date: Sat, 5 Oct 2024 00:40:38 +0200
From: Caleb Connolly <caleb.connolly@...aro.org>
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>,
John Ogness <john.ogness@...utronix.de>,
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
Subject: Re: [PATCH v3 0/4] drm/log: Introduce a new boot logger to draw the
kmsg on the screen
Hi Jocelyn,
On 10/09/2024 08:56, Jocelyn Falempe wrote:
> drm_log is a simple logger that uses the drm_client API to print the kmsg boot log on the screen.
> This is not a full replacement to fbcon, as it will only print the kmsg.
> It will never handle user input, or a terminal because this is better done in userspace.
I tried this out on the OnePlus 6 (Qualcomm SDM845/freedreno) and it
looks great :D
Here's a demo for kicks:
https://people.linaro.org/~caleb.connolly/drm_log_oneplus6.mp4
Tested-by: Caleb Connolly <caleb.connolly@...aro.org> # freedreno/dsi
Kind regards,
>
> If you're curious on how it looks like, I've put a small demo here:
> https://people.redhat.com/jfalempe/drm_log/drm_log_draft_boot_v2.mp4
>
> Design decisions:
> * It uses the drm_client API, so it should work on all drm drivers from the start.
> * It doesn't scroll the message, that way it doesn't need to redraw the whole screen for each new message.
> It also means it doesn't have to keep drawn messages in memory, to redraw them when scrolling.
> * drm_log can only be built-in (and drm must be built-in too).
> The reason is that, if you build it as a module, then a userspace application will be more appropriate than this module.
> * It uses the new non-blocking console API, so it should work well with PREEMPT_RT
>
> v2:
> * Use vmap_local() api, with that change, I've tested it successfully on simpledrm, virtio-gpu, amdgpu, and nouveau.
> * Stop drawing when the drm_master is taken. This avoid wasting CPU cycle if the buffer is not visible.
> * Use deferred probe. Only do the probe the first time there is a log to draw. With this, if you boot with quiet, drm_log won't do any modeset.
> * Add color support for the timestamp prefix, like what dmesg does.
> * Add build dependency on disabling the fbdev emulation, as they are both drm_client, and there is no way to choose which one gets the focus.
>
> v3:
> * Remove the work thread and circular buffer, and use the new write_thread() console API.
> * Register a console for each drm driver.
>
> Thanks and best regards,
>
> Jocelyn Falempe (4):
> drm/panic: Move drawing functions to drm_draw
> drm/log: Introduce a new boot logger to draw the kmsg on the screen
> drm/log: Do not draw if drm_master is taken
> drm/log: Color the timestamp, to improve readability
>
> drivers/gpu/drm/Kconfig | 19 ++
> drivers/gpu/drm/Makefile | 3 +
> drivers/gpu/drm/drm_draw.c | 216 ++++++++++++++++++++
> drivers/gpu/drm/drm_draw.h | 56 ++++++
> drivers/gpu/drm/drm_drv.c | 2 +
> drivers/gpu/drm/drm_log.c | 391 ++++++++++++++++++++++++++++++++++++
> drivers/gpu/drm/drm_log.h | 11 +
> drivers/gpu/drm/drm_panic.c | 247 +++--------------------
> 8 files changed, 721 insertions(+), 224 deletions(-)
> create mode 100644 drivers/gpu/drm/drm_draw.c
> create mode 100644 drivers/gpu/drm/drm_draw.h
> create mode 100644 drivers/gpu/drm/drm_log.c
> create mode 100644 drivers/gpu/drm/drm_log.h
>
>
> base-commit: 9aaeb87ce1e966169a57f53a02ba05b30880ffb8
--
// Caleb (they/them)
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