Add an EGLDevice type attribute

[emersion]

Vulkan has VkPhysicalDeviceType which indicates what kind of device the VkPhysicalDevice is. It would be useful to add something similar to EGLDevice. (I personally need to figure out whether it's a software-based renderer, and check for EGL_MESA_device_software for now.)

[stonesthrow]

@cubanismo - add James for his interest in EGLDevice.

[emersion]

Gentle ping @cubanismo

[cubanismo]

I don't have much to add. There's some debate around the Vulkan equivalent over how much apps should be reading into device type, especially for the "virtual" one (E.g., is a "virtual" GPU necessarily slower? E.g., is a non-virtual iGPU faster than a virtual dGPU? Is a pass-through PCI device considered a "virtual" GPU?), but it's there and this probably isn't going to be any worse. If you want to make it an EXT, I'm happy to sign on from the NV side.

[emersion]

If you believe "virtual" should be omitted, I'd be happy to leave it out. Thanks for the feedback!

[stonesthrow]

Question: Is software vs hardware vs virtual the key? or are you trying to compare performance, to select the most performant option?

[emersion]

Personally I'm only interested in checking whether it's a software implementation. I'm writing Wayland compositors, so the whole desktop will be super sluggish if a software implementation is used (e.g. because the driver doesn't support new hardware, or because the user forgot to install the correct driver). I want users to opt-in to software rendering if they really want to use that, since that'll almost always indicate something wrong. I've received a number of bug reports about confused users not understanding why everything is so slow, or why their battery dry up so quickly.

[stonesthrow]

There could be a number of things useful - local host CPU, would impact CPU use - verses a discrete GPU, maybe GPU flops metric would indicate a certain level of performance - to compare more than one device option. Just looking for what is most informative/useful for the need. The VkPhysicalDeviceType covers a lot of this, but if you have 2 GPUs, could you select the more performant? (integrated vs discrete). Is this similar to VkPhysicalDeviceType - enough? Makes it easy if Vulkan is your backend. I don't think there is a clear and easy way to provide performance, so lets go for something compatible with VkPhysicalDeviceType

[emersion]

I already have a GPU selected before-hand. I'm creating one EGL context per DRM device node. I'm just interested to know whether the EGL device matching my DRM device is backed by a real hardware driver instead of a software renderer. I'm not interested in knowing which GPU is "most performant" for my use-case.