Support VK_IMAGE_USAGE_STORAGE_BIT for WSI swapchain surfaces

Submitted by Niklas Haas

Assigned to Jason Ekstrand @jekstrand

Description

It would appear as though RADV (and ANV, judging by the code) on both X11 and Wayland only support the following hard-coded list of VkImageUsageFlags:

caps->supportedUsageFlags = VK_IMAGE_USAGE_TRANSFER_SRC_BIT | VK_IMAGE_USAGE_SAMPLED_BIT | VK_IMAGE_USAGE_TRANSFER_DST_BIT | VK_IMAGE_USAGE_COLOR_ATTACHMENT_BIT;

Could we get VK_IMAGE_USAGE_STORAGE_BIT added to this list? Other Vulkan implementations I looked at (NVIDIA and AMDVLK) both support it, and simply adding it to the list seems to work just fine for me. (on RADV+X11, not sure about ANV or Wayland)

Use case: I have a rendering pipeline (mpv/vlc/libplacebo) that may involve the use of a compute shader during the final output step, in order to do HDR peak detection. If the swapchain image supports STORAGE_BIT then I can directly paint to screen without needing to allocate an intermediate texture and roundtrip through a fragment shader unnecessarily.

Version: git

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