Re: [PATCH] drm/msm/dpu: advertise linear-only modifiers on platforms without UBWC

[Nabige Aala <nabige.aala@oss.qualcomm.com>]

On 8/19/2026 4:53 PM, Mahadevan P wrote:
> Certain Qualcomm targets like QCM2290 and Shikra do not have UBWC
> support. On such targets, advertising DRM_FORMAT_MOD_QCOM_COMPRESSED
> in the supported modifier list causes userspace to attempt UBWC
> allocations that the kernel rejects:
>
>    msm_dpu: [drm] *ERROR* unsupported format modifier 500000000000003
>    msm_dpu: [drm] *ERROR* unsupported pixel format: AR24 little-endian
>
> On platforms without UBWC, only advertise DRM_FORMAT_MOD_LINEAR to
> avoid exposing formats that the hardware cannot handle.
>
> Fixes: 71c5c23be874 ("drm/msm/dpu: check ubwc support before adding compressed formats")
> Signed-off-by: Mahadevan P <mahadevan.p@oss.qualcomm.com>
> ---
>   drivers/gpu/drm/msm/disp/dpu1/dpu_plane.c | 10 +++++++++-
>   1 file changed, 9 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_plane.c b/drivers/gpu/drm/msm/disp/dpu1/dpu_plane.c
> index 7b92082d35a6..c8bd034690cb 100644
> --- a/drivers/gpu/drm/msm/disp/dpu1/dpu_plane.c
> +++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_plane.c
> @@ -94,6 +94,11 @@ static const uint64_t supported_format_modifiers[] = {
>   	DRM_FORMAT_MOD_INVALID
>   };
>   
> +static const uint64_t supported_format_modifiers_no_ubwc[] = {
> +	DRM_FORMAT_MOD_LINEAR,
> +	DRM_FORMAT_MOD_INVALID
> +};
> +
>   #define to_dpu_plane(x) container_of(x, struct dpu_plane, base)
>   
>   static struct dpu_kms *_dpu_plane_get_kms(struct drm_plane *plane)
> @@ -1836,7 +1841,10 @@ static struct drm_plane *dpu_plane_init_common(struct drm_device *dev,
>   	pdpu = drmm_universal_plane_alloc(dev, struct dpu_plane, base,
>   				0xff, &dpu_plane_funcs,
>   				format_list, num_formats,
> -				supported_format_modifiers, type, NULL);
> +				(kms->mdss->ubwc_enc_version == 0) ?
> +					supported_format_modifiers_no_ubwc :
> +					supported_format_modifiers,

Can we just pass the NULL here in case no ubwc modifer are supported 
instead of "supported_format_modifier_no_ubwc"?

would not it automatically handled in this function 
__drm_universal_plane_init as default_modifier?

Thanks,

Nabige

> +				type, NULL);
>   	if (IS_ERR(pdpu))
>   		return ERR_CAST(pdpu);
>   
>
> ---
> base-commit: e6664f2b33db9b6811eb4cec109f06cb2b4f458d
> change-id: 20260819-remove_ubwc-0180dfb2908c
>
> Best regards,