Re: [PATCH v3 0/4] drm/log: Introduce a new boot logger to draw the kmsg on the screen

[Jocelyn Falempe]

On 05/10/2024 00:40, Caleb Connolly wrote:
> 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

Thanks, it's a really nice demo!
For high-resolution screen, I will add integer scaling soon, so that 
should be a bit easier to read, without requiring huge fonts.

--

Jocelyn


> Tested-by: Caleb Connolly <caleb.connolly@xxxxxxxxxx> # 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