Re: [PATCH v6 23/25] drm/xe: Compute dumb-buffer sizes with drm_mode_size_dumb()

Lucas De Marchi
2025-09-29T15:25:49Z

On Thu, Aug 21, 2025 at 10:17:30AM +0200, Thomas Zimmermann wrote:
>Call drm_mode_size_dumb() to compute dumb-buffer scanline pitch
>and buffer size. Align the pitch to a multiple of 8. Align the
>buffer size according to hardware requirements.
>
>Xe's internal calculation allowed for 64-bit wide buffer sizes, but
>the ioctl's internal checks always verified against 32-bit wide limits.
>Hance, it is safe to limit the driver code to 32-bit calculations as
>well.
>
>v3:
>- mention 32-bit calculation in commit description (Matthew)
>
>Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
>Reviewed-by: Matthew Auld <matthew.auld@intel.com>
>Cc: Lucas De Marchi <lucas.demarchi@intel.com>
>Cc: "Thomas Hellström" <thomas.hellstrom@linux.intel.com>
>Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>

Acked-by: Lucas De Marchi <lucas.demarchi@intel.com>

to merge this via drm-misc.

thanks
Lucas De Marchi

>---
> drivers/gpu/drm/xe/xe_bo.c | 8 ++++----
> 1 file changed, 4 insertions(+), 4 deletions(-)
>
>diff --git a/drivers/gpu/drm/xe/xe_bo.c b/drivers/gpu/drm/xe/xe_bo.c
>index 6fea39842e1e..2be7a618165a 100644
>--- a/drivers/gpu/drm/xe/xe_bo.c
>+++ b/drivers/gpu/drm/xe/xe_bo.c
>@@ -9,6 +9,7 @@
> #include <linux/nospec.h>
>
> #include <drm/drm_drv.h>
>+#include <drm/drm_dumb_buffers.h>
> #include <drm/drm_gem_ttm_helper.h>
> #include <drm/drm_managed.h>
> #include <drm/ttm/ttm_backup.h>
>@@ -3130,14 +3131,13 @@ int xe_bo_dumb_create(struct drm_file *file_priv,
> struct xe_device *xe = to_xe_device(dev);
> struct xe_bo *bo;
> uint32_t handle;
>- int cpp = DIV_ROUND_UP(args->bpp, 8);
> int err;
> u32 page_size = max_t(u32, PAGE_SIZE,
> xe->info.vram_flags & XE_VRAM_FLAGS_NEED64K ? SZ_64K : SZ_4K);
>
>- args->pitch = ALIGN(args->width * cpp, 64);
>- args->size = ALIGN(mul_u32_u32(args->pitch, args->height),
>- page_size);
>+ err = drm_mode_size_dumb(dev, args, SZ_64, page_size);
>+ if (err)
>+ return err;
>
> bo = xe_bo_create_user(xe, NULL, NULL, args->size,
> DRM_XE_GEM_CPU_CACHING_WC,
>--
>2.50.1
>