Re: [PATCH v4 03/25] drm/gem-dma: Compute dumb-buffer sizes with drm_mode_size_dumb()

[Tomi Valkeinen <tomi.valkeinen@xxxxxxxxxxxxxxxx>]

Hi,

On 11/03/2025 17:47, 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.
> 
> Push the current calculation into the only direct caller imx. Imx's
> hardware requires the framebuffer width to be aligned to 8. The
> driver's current approach is actually incorrect, as it only guarantees
> this implicitly and requires bpp to be a multiple of 8 already. A
> later commit will fix this problem by aligning the scanline pitch
> such that an aligned width still fits into each scanline's memory.
> 
> A number of other drivers are build on top of gem-dma helpers and
> implement their own dumb-buffer allocation. These drivers invoke
> drm_gem_dma_dumb_create_internal(), which is not affected by this
> commit.
> 
> Signed-off-by: Thomas Zimmermann <tzimmermann@xxxxxxx>
> ---
>  drivers/gpu/drm/drm_gem_dma_helper.c     | 7 +++++--
>  drivers/gpu/drm/imx/ipuv3/imx-drm-core.c | 2 ++
>  2 files changed, 7 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/drm_gem_dma_helper.c 
> b/drivers/gpu/drm/drm_gem_dma_helper.c
> index b7f033d4352a..49be9b033610 100644
> --- a/drivers/gpu/drm/drm_gem_dma_helper.c
> +++ b/drivers/gpu/drm/drm_gem_dma_helper.c
> @@ -20,6 +20,7 @@
>  #include <drm/drm.h>
>  #include <drm/drm_device.h>
>  #include <drm/drm_drv.h>
> +#include <drm/drm_dumb_buffers.h>
>  #include <drm/drm_gem_dma_helper.h>
>  #include <drm/drm_vma_manager.h>
>  
> @@ -304,9 +305,11 @@ int drm_gem_dma_dumb_create(struct drm_file *file_priv,
>                           struct drm_mode_create_dumb *args)
>  {
>       struct drm_gem_dma_object *dma_obj;
> +     int ret;
>  
> -     args->pitch = DIV_ROUND_UP(args->width * args->bpp, 8);
> -     args->size = args->pitch * args->height;
> +     ret = drm_mode_size_dumb(drm, args, SZ_8, 0);
> +     if (ret)
> +             return ret;
>  
>       dma_obj = drm_gem_dma_create_with_handle(file_priv, drm, args->size,
>                                                &args->handle);
> diff --git a/drivers/gpu/drm/imx/ipuv3/imx-drm-core.c 
> b/drivers/gpu/drm/imx/ipuv3/imx-drm-core.c
> index ec5fd9a01f1e..e7025df7b978 100644
> --- a/drivers/gpu/drm/imx/ipuv3/imx-drm-core.c
> +++ b/drivers/gpu/drm/imx/ipuv3/imx-drm-core.c
> @@ -145,6 +145,8 @@ static int imx_drm_dumb_create(struct drm_file *file_priv,
>       int ret;
>  
>       args->width = ALIGN(width, 8);
> +     args->pitch = DIV_ROUND_UP(args->width * args->bpp, 8);
> +     args->size = args->pitch * args->height;
>  
>       ret = drm_gem_dma_dumb_create(file_priv, drm, args);
>       if (ret)

Won't the pitch and size just be overwritten by the
drm_gem_dma_dumb_create() call?

 Tomi