Re: [PATCH v4] dma-buf: Add a capabilities directory

On Thu, Jun 02, 2022 at 08:47:56AM +0200, Daniel Vetter wrote:

Two expand on this:

• compositor opens the drm render /dev node
• compositor initializes the opengl or vulkan userspace driver on top of that
• compositor asks that userspace driver to allocate some buffer, which

can be pretty expensive

• compositor asks the userspace driver to export that buffer into a dma-buf
• compositor can finally do the test ioctl, realizes support isn't

there and tosses the entire thing

read() on a sysfs file is so much more reasonable it's not even funny.

What about dma-buf heaps? That should be a shorter route to getting a dma-buf fd if that's all that's needed.

Cheers, -Brian