Re: [PATCH v6 00/25] drm/dumb-buffers: Fix and improve buffer-size calculation

Thomas Zimmermann
2025-09-15T10:35:29Z

FYI, I significant number of these patches got a review already. I
intent to merge these and then send out the others for each driver
individually.

Am 21.08.25 um 10:17 schrieb Thomas Zimmermann:
> Dumb-buffer pitch and size is specified by width, height, bits-per-pixel
> plus various hardware-specific alignments. The calculation of these
> values is inconsistent and duplicated among drivers. The results for
> formats with bpp < 8 are sometimes incorrect.
>
> This series fixes this for most drivers. Default scanline pitch and
> buffer size are now calculated with the existing 4CC helpers. There is
> a new helper drm_mode_size_dumb() that calculates scanline pitch and
> buffer size according to driver requirements.
>
> The series fixes the common GEM implementations for DMA, SHMEM and
> VRAM. It further changes most implementations of dumb_create to use
> the new helper. A small number of drivers has more complicated
> calculations and will be updated by a later patches.
>
> v6:
> - extend TODO item (Tomi)
> - fix typos in documentation (Tomi)
> v5:
> - use check_mul_overflow() for overflow test (Tomi)
> - imx: fix intermediate code (Tomi)
> - rz-du: include dumb-buffers header
> v4:
> - improve UAPI documentation
> - document bpp special cases
> - use drm_warn_once()
> - add TODO lists
> - armada: fix pitch alignment
> v3:
> - document UAPI semantics
> - fall back to bpp-based allocation for unknown color modes
> - cleanups
> v2:
> - rewrite series
> - convert many individual drivers besides the shared GEM helpers
>
> Thomas Zimmermann (25):
> drm/dumb-buffers: Sanitize output on errors
> drm/dumb-buffers: Provide helper to set pitch and size
> drm/gem-dma: Compute dumb-buffer sizes with drm_mode_size_dumb()
> drm/gem-shmem: Compute dumb-buffer sizes with drm_mode_size_dumb()
> drm/gem-vram: Compute dumb-buffer sizes with drm_mode_size_dumb()
> drm/armada: Compute dumb-buffer sizes with drm_mode_size_dumb()
> drm/exynos: Compute dumb-buffer sizes with drm_mode_size_dumb()
> drm/gma500: Compute dumb-buffer sizes with drm_mode_size_dumb()
> drm/hibmc: Compute dumb-buffer sizes with drm_mode_size_dumb()
> drm/imx/ipuv3: Compute dumb-buffer sizes with drm_mode_size_dumb()
> drm/loongson: Compute dumb-buffer sizes with drm_mode_size_dumb()
> drm/mediatek: Compute dumb-buffer sizes with drm_mode_size_dumb()
> drm/msm: Compute dumb-buffer sizes with drm_mode_size_dumb()
> drm/nouveau: Compute dumb-buffer sizes with drm_mode_size_dumb()
> drm/omapdrm: Compute dumb-buffer sizes with drm_mode_size_dumb()
> drm/qxl: Compute dumb-buffer sizes with drm_mode_size_dumb()
> drm/renesas/rcar-du: Compute dumb-buffer sizes with
> drm_mode_size_dumb()
> drm/renesas/rz-du: Compute dumb-buffer sizes with drm_mode_size_dumb()
> drm/rockchip: Compute dumb-buffer sizes with drm_mode_size_dumb()
> drm/tegra: Compute dumb-buffer sizes with drm_mode_size_dumb()
> drm/virtio: Compute dumb-buffer sizes with drm_mode_size_dumb()
> drm/vmwgfx: Compute dumb-buffer sizes with drm_mode_size_dumb()
> drm/xe: Compute dumb-buffer sizes with drm_mode_size_dumb()
> drm/xen: Compute dumb-buffer sizes with drm_mode_size_dumb()
> drm/xlnx: Compute dumb-buffer sizes with drm_mode_size_dumb()
>
> Documentation/gpu/todo.rst | 37 ++++
> drivers/gpu/drm/armada/armada_gem.c | 16 +-
> drivers/gpu/drm/drm_dumb_buffers.c | 170 ++++++++++++++++--
> drivers/gpu/drm/drm_gem_dma_helper.c | 7 +-
> drivers/gpu/drm/drm_gem_shmem_helper.c | 16 +-
> drivers/gpu/drm/drm_gem_vram_helper.c | 89 +++------
> drivers/gpu/drm/exynos/exynos_drm_gem.c | 8 +-
> drivers/gpu/drm/gma500/gem.c | 21 +--
> .../gpu/drm/hisilicon/hibmc/hibmc_drm_drv.c | 25 ++-
> drivers/gpu/drm/imx/ipuv3/imx-drm-core.c | 29 ++-
> drivers/gpu/drm/loongson/lsdc_gem.c | 29 +--
> drivers/gpu/drm/mediatek/mtk_gem.c | 13 +-
> drivers/gpu/drm/msm/msm_gem.c | 27 ++-
> drivers/gpu/drm/nouveau/nouveau_display.c | 7 +-
> drivers/gpu/drm/omapdrm/omap_gem.c | 15 +-
> drivers/gpu/drm/qxl/qxl_dumb.c | 17 +-
> drivers/gpu/drm/renesas/rcar-du/rcar_du_kms.c | 7 +-
> drivers/gpu/drm/renesas/rz-du/rzg2l_du_kms.c | 8 +-
> drivers/gpu/drm/rockchip/rockchip_drm_gem.c | 12 +-
> drivers/gpu/drm/tegra/gem.c | 8 +-
> drivers/gpu/drm/virtio/virtgpu_gem.c | 11 +-
> drivers/gpu/drm/vmwgfx/vmwgfx_surface.c | 21 +--
> drivers/gpu/drm/xe/xe_bo.c | 8 +-
> drivers/gpu/drm/xen/xen_drm_front.c | 7 +-
> drivers/gpu/drm/xlnx/zynqmp_kms.c | 7 +-
> include/drm/drm_dumb_buffers.h | 14 ++
> include/drm/drm_gem_vram_helper.h | 6 -
> include/uapi/drm/drm_mode.h | 50 +++++-
> 28 files changed, 457 insertions(+), 228 deletions(-)
> create mode 100644 include/drm/drm_dumb_buffers.h
>

--
--
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Frankenstrasse 146, 90461 Nuernberg, Germany
GF: Ivo Totev, Andrew Myers, Andrew McDonald, Boudien Moerman
HRB 36809 (AG Nuernberg)