allow access to queue family index in vulkan hal device (gfx-rs#2859)

CHANGELOG.md

@@ -56,6 +56,10 @@ Bottom level categories:
 - Fix depth stencil texture format capability by @jinleili in [#2854](https://github.com/gfx-rs/wgpu/pull/2854)
 - `get_texture_format_features` now only returns usages for formats it actually supports by @cwfitzgerald in [#2856](https://github.com/gfx-rs/wgpu/pull/2856)
 
+#### Hal
+
+- Allow access to queue family index in Vulkan hal by @i509VCB in [#2859](https://github.com/gfx-rs/wgpu/pull/2859)
+
 ### Documentation
 - Update present_mode docs as most of them don't automatically fall back to Fifo anymore. by @Elabajaba in [#2855](https://github.com/gfx-rs/wgpu/pull/2855)
 

wgpu-hal/src/vulkan/adapter.rs

@@ -1316,6 +1316,7 @@ impl super::Adapter {
 
         let shared = Arc::new(super::DeviceShared {
             raw: raw_device,
+            family_index,
             handle_is_owned,
             instance: Arc::clone(&self.instance),
             physical_device: self.raw,

wgpu-hal/src/vulkan/device.rs

@@ -702,6 +702,15 @@ impl super::Device {
         })
     }
 
+    /// Returns the queue family index of the device's internal queue.
+    ///
+    /// This is useful for constructing memory barriers needed for queue family ownership transfer when
+    /// external memory is involved (from/to `VK_QUEUE_FAMILY_EXTERNAL_KHR` and `VK_QUEUE_FAMILY_FOREIGN_EXT`
+    /// for example).
+    pub fn queue_family_index(&self) -> u32 {
+        self.shared.family_index
+    }
+
     pub fn raw_device(&self) -> &ash::Device {
         &self.shared.raw
     }

wgpu-hal/src/vulkan/mod.rs

@@ -312,6 +312,7 @@ impl UpdateAfterBindTypes {
 
 struct DeviceShared {
     raw: ash::Device,
+    family_index: u32,
     handle_is_owned: bool,
     instance: Arc<InstanceShared>,
     physical_device: ash::vk::PhysicalDevice,