Function sampleable_modifiers 

pub fn sampleable_modifiers(device: &Device, fourcc: u32) -> Vec<u64>

The DRM modifiers device can sample for a single-plane dma-buf of fourcc: each one the driver lists for the format and confirms (VulkanImporter::check_modifier, the check every import repeats at its real size) can be imported and sampled. Empty when the device is not Vulkan, lacks VK_EXT_image_drm_format_modifier, or has no such format.

A compositor advertises exactly these (beyond the linear layout it reads on the CPU), so a client can only pick a layout the import will accept.