Fix: Error output is not require, VK_QUEUE_TRANSFER_BIT is optional.

[Alex2782]

Fixes #99412

A queue family with the requested bits could not be found.

https://registry.khronos.org/vulkan/specs/1.3-extensions/man/html/VkQueueFlagBits.html

...reporting the VK_QUEUE_TRANSFER_BIT capability separately for that queue family is optional.

[Alex2782]

Note: it's not a critical error, everything works so far. The error message constantly appears in the Android editor as soon as a project is started. (also Logcat - Android Studio)

Tested also on MacMini M1 Molten / Vulkan, VK_QUEUE_TRANSFER_BIT is available there.

godot/servers/rendering/rendering_device.cpp

Lines 6142 to 6150 in fd4c29a

	transfer_queue_family = driver->command_queue_family_get(RDD::COMMAND_QUEUE_FAMILY_TRANSFER_BIT);
	if (transfer_queue_family) {
	// Create the transfer queue.
	transfer_queue = driver->command_queue_create(transfer_queue_family);
	ERR_FAIL_COND_V(!transfer_queue, FAILED);
	} else {
	// Use main queue as the transfer queue.
	transfer_queue = main_queue;
	transfer_queue_family = main_queue_family;

[DarioSamo]

I'm afraid this seems like the wrong way to fix the problem and it just adds more complexity to code that shouldn't have it.

If the issue is that the error message shows up, then I suggest making a PR to handle this...

ERR_FAIL_COND_V_MSG(picked_family_index >= queue_family_properties.size(), CommandQueueFamilyID(), "A queue family with the requested bits could not be found.");

...as a correct case instead and just make it return the empty Id without printing an error.

To further support that, the code that calls this already handles the empty Id properly:

godot/servers/rendering/rendering_device.cpp

Lines 6142 to 6151 in fd4c29a

	transfer_queue_family = driver->command_queue_family_get(RDD::COMMAND_QUEUE_FAMILY_TRANSFER_BIT);
	if (transfer_queue_family) {
	// Create the transfer queue.
	transfer_queue = driver->command_queue_create(transfer_queue_family);
	ERR_FAIL_COND_V(!transfer_queue, FAILED);
	} else {
	// Use main queue as the transfer queue.
	transfer_queue = main_queue;
	transfer_queue_family = main_queue_family;
	}

So to me it just looks like a case of an error message that shouldn't be printed.

[DarioSamo]

Change looks good to me now.

For your consideration as well: now that we're properly requesting it like this and we're fully aware Android does not cover this case, it might be worth considering to add code to RenderingDevice when it requests the transfer family to attempt to get a compute queue instead if it fails to find it.

As it is now, the code will just fall back to the graphics queue. However, the existence of the compute bit implies the capability of transfer, so it should be possible to use asynchronous compute queues if they're supported.

I don't think a check like that needs to be part of this PR, and I think it's subject to some testing if it actually gives much of a benefit on Android devices.

[Calinou]

Tested locally on Samsung Galaxy Z Fold4 (Android 14), it works as expected. I used to get an error on startup before this change.

[Alex2782]

... However, the existence of the compute bit implies the capability of transfer, so it should be possible to use asynchronous compute queues if they're supported.

... and I think it's subject to some testing if it actually gives much of a benefit on Android devices.

Android devices with multiple queue families are very rare (and very expensive).
Such smartphones have only been available for a few weeks. It will probably only be worth looking into it in more detail in 2 to 3 years.

Adreno (TM) 830 (like Xiaomi 15 (Pro) for 900+ €)
https://vulkan.gpuinfo.org/displayreport.php?id=34702#queuefamilies

screenshots

[akien-mga]

Thanks!