Re: [PATCH 3/3] drm/panic: Add a kconfig option to dump kunits results to png
From: Jocelyn Falempe
Date: Mon Sep 01 2025 - 09:16:39 EST
On 27/08/2025 11:52, Maxime Ripard wrote:
Hi,
On Thu, Aug 21, 2025 at 11:49:07AM +0200, Jocelyn Falempe wrote:
This is a bit hacky, but very handy if you want to customize the
panic screen.
It allows to dump the generated images to the logs, and then a python
script can convert it to .png files. It makes it easy to check how
the panic screen will look on different resolutions, without having
to crash a VM.
To not pollute the logs, it uses a monochrome framebuffer, compress
it with zlib, and base64 encode it.
Signed-off-by: Jocelyn Falempe <jfalempe@xxxxxxxxxx>
---
drivers/gpu/drm/Kconfig.debug | 14 ++++
drivers/gpu/drm/tests/drm_panic_test.c | 111 +++++++++++++++++++++++++
scripts/kunitpanic2png.py | 53 ++++++++++++
3 files changed, 178 insertions(+)
create mode 100755 scripts/kunitpanic2png.py
diff --git a/drivers/gpu/drm/Kconfig.debug b/drivers/gpu/drm/Kconfig.debug
index 05dc43c0b8c5..d8ae85132d32 100644
--- a/drivers/gpu/drm/Kconfig.debug
+++ b/drivers/gpu/drm/Kconfig.debug
@@ -84,6 +84,20 @@ config DRM_KUNIT_TEST
If in doubt, say "N".
+config DRM_PANIC_KUNIT_TEST_DUMP
+ bool "Enable screen dump to logs in KUnit tests for drm_panic"
+ default n
+ depends on DRM && DRM_PANIC && DRM_KUNIT_TEST
+ select ZLIB_DEFLATE
+ help
+ This allows to dump the panic screen to the KUnit tests logs.
+ It's possible with a small python script to write pngs from the logs.
+
+ This is only to help developers customizing the drm_panic screen,
+ checking the result for different resolutions.
+
+ If in doubt, say "N"
+
config DRM_TTM_KUNIT_TEST
tristate "KUnit tests for TTM" if !KUNIT_ALL_TESTS
default n
diff --git a/drivers/gpu/drm/tests/drm_panic_test.c b/drivers/gpu/drm/tests/drm_panic_test.c
index 46ff3e5e0e5d..8cddb845aea9 100644
--- a/drivers/gpu/drm/tests/drm_panic_test.c
+++ b/drivers/gpu/drm/tests/drm_panic_test.c
@@ -115,24 +115,135 @@ static void drm_test_panic_screen_user_page(struct kunit *test)
kfree(pages);
}
+#ifdef CONFIG_DRM_PANIC_KUNIT_TEST_DUMP
+#include <linux/base64.h>
+#include <linux/delay.h>
+#include <linux/zlib.h>
+
+#define LINE_LEN 128
+
+#define COMPR_LEVEL 6
+#define WINDOW_BITS 12
+#define MEM_LEVEL 4
+
+static int compress_image(u8 *src, int size, u8 *dst)
+{
+ struct z_stream_s stream;
+
+ stream.workspace = kmalloc(zlib_deflate_workspacesize(WINDOW_BITS, MEM_LEVEL),
+ GFP_KERNEL);
+
+ if (zlib_deflateInit2(&stream, COMPR_LEVEL, Z_DEFLATED, WINDOW_BITS,
+ MEM_LEVEL, Z_DEFAULT_STRATEGY) != Z_OK)
+ return -EINVAL;
+
+ stream.next_in = src;
+ stream.avail_in = size;
+ stream.total_in = 0;
+ stream.next_out = dst;
+ stream.avail_out = size;
+ stream.total_out = 0;
+
+ if (zlib_deflate(&stream, Z_FINISH) != Z_STREAM_END)
+ return -EINVAL;
+
+ if (zlib_deflateEnd(&stream) != Z_OK)
+ return -EINVAL;
+
+ kfree(stream.workspace);
+
+ return stream.total_out;
+}
+
+static void dump_image(u8 *fb, unsigned int width, unsigned int height)
+{
+ int len = 0;
+ char *dst;
+ char *compressed;
+ int sent = 0;
+ int stride = DIV_ROUND_UP(width, 8);
+ int size = stride * height;
+
+ compressed = vzalloc(size);
+ if (!compressed)
+ return;
+ len = compress_image(fb, size, compressed);
+ if (len < 0) {
+ pr_err("Compression failed %d", len);
+ return;
+ }
+
+ dst = vzalloc(4 * DIV_ROUND_UP(len, 3) + 1);
+ if (!dst)
+ return;
+
+ len = base64_encode(compressed, len, dst);
+
+ pr_info("KUNIT PANIC IMAGE DUMP START %dx%d", width, height);
+ while (len > 0) {
+ char save = dst[sent + LINE_LEN];
+
+ dst[sent + LINE_LEN] = 0;
+ pr_info("%s", dst + sent);
+ dst[sent + LINE_LEN] = save;
+ sent += LINE_LEN;
+ len -= LINE_LEN;
+ }
+ pr_info("KUNIT PANIC IMAGE DUMP END");
The kunit test output format is defined, and we should probably use a
diagnostic line for this:
https://docs.kernel.org/dev-tools/ktap.html#diagnostic-lines
We should probably cc the kunit maintainers about this too.
Thanks for the pointer, I will also experiment with debugfs, as
suggested by Thomas.
Best regards,
--
Jocelyn
Maxime