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([2a01:e0a:11aa:87f0:935:4f8e:b423:64eb]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-482b145d31bsm13853815f8f.16.2026.08.20.10.49.39 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 20 Aug 2026 10:49:39 -0700 (PDT) Message-ID: Date: Thu, 20 Aug 2026 19:49:36 +0200 Precedence: bulk X-Mailing-List: linux-doc@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 00/12] drm/panic: Split into core and helpers To: Thomas Zimmermann , javierm@redhat.com, airlied@gmail.com, simona@ffwll.ch, maarten.lankhorst@linux.intel.com, mripard@kernel.org Cc: dri-devel@lists.freedesktop.org, linux-doc@vger.kernel.org, amd-gfx@lists.freedesktop.org, rust-for-linux@vger.kernel.org, linux-hyperv@vger.kernel.org, intel-gfx@lists.freedesktop.org, intel-xe@lists.freedesktop.org, imx@lists.linux.dev, linux-arm-kernel@lists.infradead.org, nouveau@lists.freedesktop.org, linux-renesas-soc@vger.kernel.org, virtualization@lists.linux.dev, sashiko-reviews@lists.linux.dev References: <20260818125012.468092-1-tzimmermann@suse.de> Content-Language: en-US, fr From: Jocelyn Falempe In-Reply-To: <20260818125012.468092-1-tzimmermann@suse.de> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 18/08/2026 14:27, Thomas Zimmermann wrote: > Split DRM's current panic handling into a core and a helper module. > The core is still part of DRM's core library. The panic helpers are > part of DRM's KMS helper module (for now). > > The motivation behind this series is to get panic handling's drawing > code out of the DRM core. At some point it should share a single > module with DRM's other drawing and format conversion. > > With the series applied, panic hanlding follows DRM's established > design pattern of having a DRM core interface with an dedicated > implementation in each driver. Drivers share common code in helper > modules. For panic handling, the DRM core still contains the panic > entry points, the parameters and the debugfs interface. All drawing > is now located in the panic helpers. > > Patches 1 to 4 improve several issues in the current panic code. It > makes sense to fix them before moving the core around. > > Patches 5 to 8 put handling of all panic state and locking into a > single place, drm_panic_display_panic_screen(). It is maintained by > panic handling's DRM core code. This also enables the test cases to > work more independently from the kernel's configuration. > > Patches 9 to 11 split the panic-handling code into the core and panic > helpers. The former maintain all state, locking and public interfaces. > The latter handles drawing and details of the involved framebuffers. > > DRM devices that offer panic handling provide a single callback, struct > drm_plane_funcs.display_panic_screen. A new initializer macro makes it > point to the existing panic-drawing implementation. Hence there's no > change in features or functionality. If panic handling is configured > off, it all clears out to NULL. > > Patch 12 reworks the test cases slighly, so that they can be build as > a separate module. Do 'modprobe drm_panic_helper_test' to run them. > > Tested under bochs with debugfs and test cases. Overall the series looks good to me, and I like the split between the helper and the core. I would just drop the first two patches, as I don't see much difference between static allocation or kmalloc() at init, and I think that memset() the buffers to 0 is not useful in this case. Best regards, -- Jocelyn > > Future directions: > > - Panic handling shares some drawing code with format conversion and > clients. There's even more drawing code in vkms. Later series' can > attempt to unify and harmonize all these implementations in a single > draw module. > > - The drawing helper drm_plane_helper_display_panic_screen() still > implements various access schemes (map, set_pixel, memcpy) in a single > function. It could be split up into specifialized helpers. > > - If we ever need a driver-specific helper, it is now possible to > implement a custom version of display_panic_screen. > > Thomas Zimmermann (12): > drm/panic: Allocate QR-code buffers statically > drm/panic: Make allocation of zlib workspace more robust > drm/panic: Return -EINVAL if font is not available > drm/panic: Return errno codes if panic output fails > drm/panic: Pass colors to draw_panic_dispatch() > drm/panic: Pass global module parameters to drm_panic_dispatch() > drm/panic: Retry in dispatch function if panic output fails > drm/panic: Split draw_panic_plane() > drm/panic: Display panic screen via per-plane callback > drm/panic: Internalize panic locking in DRM core and helpers > drm/panic: Move panic display code into helper library > drm/panic: Compile KUnit tests as module > > Documentation/gpu/drm-kms-helpers.rst | 11 +- > Documentation/gpu/drm-kms.rst | 3 + > MAINTAINERS | 11 +- > drivers/gpu/drm/Kconfig | 5 + > drivers/gpu/drm/Kconfig.debug | 1 + > drivers/gpu/drm/Makefile | 3 +- > .../amd/display/amdgpu_dm/amdgpu_dm_plane.c | 2 + > drivers/gpu/drm/ast/ast_mode.c | 2 + > drivers/gpu/drm/drm_atomic_helper.c | 2 +- > drivers/gpu/drm/drm_crtc_internal.h | 2 - > drivers/gpu/drm/drm_drv.c | 3 +- > drivers/gpu/drm/drm_kms_helper_common.c | 14 + > drivers/gpu/drm/drm_panic.c | 914 +---------------- > drivers/gpu/drm/drm_panic_helper.c | 915 ++++++++++++++++++ > ...drm_panic_qr.rs => drm_panic_helper_qr.rs} | 4 +- > drivers/gpu/drm/drm_panic_internal.h | 59 ++ > drivers/gpu/drm/hyperv/hyperv_drm_modeset.c | 2 + > drivers/gpu/drm/i915/display/i9xx_plane.c | 3 + > .../drm/i915/display/skl_universal_plane.c | 4 + > drivers/gpu/drm/imx/ipuv3/ipuv3-plane.c | 2 + > drivers/gpu/drm/mgag200/mgag200_drv.h | 4 +- > drivers/gpu/drm/nouveau/dispnv50/wndw.c | 2 + > .../gpu/drm/renesas/rcar-du/rcar_du_plane.c | 2 + > .../drm/renesas/shmobile/shmob_drm_plane.c | 2 + > drivers/gpu/drm/sysfb/drm_sysfb_helper.h | 4 +- > drivers/gpu/drm/sysfb/vesadrm.c | 1 + > drivers/gpu/drm/tests/Makefile | 1 + > ...m_panic_test.c => drm_panic_helper_test.c} | 65 +- > drivers/gpu/drm/tidss/tidss_plane.c | 2 + > drivers/gpu/drm/tiny/bochs.c | 4 +- > drivers/gpu/drm/virtio/virtgpu_plane.c | 2 + > include/drm/drm_mode_config.h | 4 +- > include/drm/drm_modeset_helper_vtables.h | 11 +- > include/drm/drm_panic.h | 117 +-- > include/drm/drm_panic_helper.h | 40 + > include/drm/drm_plane.h | 57 ++ > rust/bindings/bindings_helper.h | 4 +- > 37 files changed, 1253 insertions(+), 1031 deletions(-) > create mode 100644 drivers/gpu/drm/drm_panic_helper.c > rename drivers/gpu/drm/{drm_panic_qr.rs => drm_panic_helper_qr.rs} (99%) > create mode 100644 drivers/gpu/drm/drm_panic_internal.h > rename drivers/gpu/drm/tests/{drm_panic_test.c => drm_panic_helper_test.c} (80%) > create mode 100644 include/drm/drm_panic_helper.h > > > base-commit: dc462ab791b686c48545c160ecc81be64f77a846 > prerequisite-patch-id: c67e5d886a47b7d0266d81100837557fda34cb24 > prerequisite-patch-id: a5a973e527c88a5b47053d7a72aefe0b550197cb > prerequisite-patch-id: b9adc9622920a3e70168e672c2c92795b3e3a106 > prerequisite-patch-id: 5030de433a01c2e99056cadb676a8e2ba35f055a