linux-kernel - Re: [PATCH 0/4] drm/panic: Add a qr

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Message-ID: <c1f6472a-fbf6-43db-9b44-f5fb887f3a1e@redhat.com>
Date: Thu, 4 Jul 2024 10:32:12 +0200
From: Jocelyn Falempe <jfalempe@...hat.com>
To: Greg KH <gregkh@...uxfoundation.org>
Cc: 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>,
 Miguel Ojeda <ojeda@...nel.org>, Alex Gaynor <alex.gaynor@...il.com>,
 Wedson Almeida Filho <wedsonaf@...il.com>, Boqun Feng
 <boqun.feng@...il.com>, Gary Guo <gary@...yguo.net>,
 Bjorn Roy Baron <bjorn3_gh@...tonmail.com>,
 Benno Lossin <benno.lossin@...ton.me>,
 Andreas Hindborg <a.hindborg@...sung.com>, Alice Ryhl
 <aliceryhl@...gle.com>, linux-kernel@...r.kernel.org,
 dri-devel@...ts.freedesktop.org, rust-for-linux@...r.kernel.org,
 Danilo Krummrich <dakr@...hat.com>
Subject: Re: [PATCH 0/4] drm/panic: Add a qr_code panic screen



On 04/07/2024 07:03, Greg KH wrote:
> On Wed, Jul 03, 2024 at 05:33:57PM +0200, Jocelyn Falempe wrote:
>> This series adds a new panic screen, with the kmsg data embedded in a QR-code.
>>
>> The main advantage of QR-code, is that you can copy/paste the debug data to a bug report.
>>
>> The QR-code encoder is written in rust, and is very specific to drm_panic.
>> The reason is that it is called in a panic handler, and thus can't allocate memory, or use locking.
>> The rust code uses a few rust core API, and provides only two C entry points.
>> There is no particular reason to do it in rust, I just wanted to learn rust, and see if it can work in the kernel.
>>
>> If you want to see what it looks like, I've put a few screenshots here:
>> https://github.com/kdj0c/panic_report/issues/1
> 
> Cool, this idea has been floating around for decades, here's the last
> attempt at this back in 2014:
> 	https://lore.kernel.org/all/1395093587-2583-1-git-send-email-teobaluta@gmail.com/
> 
Yes, I've looked at this, but drawing a QR-code in the middle of fbcon 
was a bit complex. Now with drm panic, there is a proper infrastructure 
to display the QR code, and make sure it won't be overwritten.

>>
>> -- 
>>
>> Jocelyn
>>
>>
>> Jocelyn Falempe (4):
>>    drm/panic: Add integer scaling to blit()
>>    drm/rect: add drm_rect_overlap()
>>    drm/panic: simplify logo handling
>>    drm/panic: Add a qr_code panic screen
>>
>>   drivers/gpu/drm/Kconfig         |  29 +
>>   drivers/gpu/drm/Makefile        |   1 +
>>   drivers/gpu/drm/drm_drv.c       |   3 +
>>   drivers/gpu/drm/drm_panic.c     | 338 +++++++++--
>>   drivers/gpu/drm/drm_panic_qr.rs | 989 ++++++++++++++++++++++++++++++++
> 
> Wait, we can put .rs files in any directory now?  I didn't think that
> worked properly yet.

Yes, thanks to the work of the rust-for-linux team. When I started to 
work on this, I needed a few workarounds to make my rust code compile. 
But since 6.10-rc1, I was able to drop them all. Also for this simple 
case, I don't use bindgen, because there are only 2 Rust functions, that 
I need to call from C.

> 
> thanks,
> 
> greg k-h
> 

-- 

Jocelyn