Properly feature gate drm support and add safety docs

wgpu-core/src/instance.rs

@@ -202,6 +202,17 @@ impl Instance {
         }
     }
 
+    /// Creates a new surface from the given drm configuration.
+    ///
+    /// # Safety
+    ///
+    /// - All parameters must point to valid DRM values.
+    ///
+    /// # Platform Support
+    ///
+    /// This function is only available on Unix-like platforms (Linux, FreeBSD) and
+    /// currently only works with the Vulkan backend.
+    #[cfg(all(unix, not(target_os = "macos")))]
     pub unsafe fn create_surface_from_drm(
         &self,
         fd: i32,
@@ -217,16 +228,28 @@ impl Instance {
         let mut surface_per_backend: HashMap<Backend, Box<dyn hal::DynSurface>> =
             HashMap::default();
 
-        let instance = unsafe { self.as_hal::<hal::api::Vulkan>() }
-            .ok_or(CreateSurfaceError::BackendNotEnabled(Backend::Vulkan))?;
-
-        match instance.create_surface_from_drm(fd, plane, connector_id, width, height, refresh_rate)
+        #[cfg(feature = "vulkan")]
         {
-            Ok(surface) => {
-                surface_per_backend.insert(Backend::Vulkan, Box::new(surface));
-            }
-            Err(err) => {
-                errors.insert(Backend::Vulkan, err);
+            let instance = unsafe { self.as_hal::<hal::api::Vulkan>() }
+                .ok_or(CreateSurfaceError::BackendNotEnabled(Backend::Vulkan))?;
+
+            // Safety must be upheld by the caller
+            match unsafe {
+                instance.create_surface_from_drm(
+                    fd,
+                    plane,
+                    connector_id,
+                    width,
+                    height,
+                    refresh_rate,
+                )
+            } {
+                Ok(surface) => {
+                    surface_per_backend.insert(Backend::Vulkan, Box::new(surface));
+                }
+                Err(err) => {
+                    errors.insert(Backend::Vulkan, err);
+                }
             }
         }
 
@@ -814,6 +837,16 @@ impl Global {
         Ok(id)
     }
 
+    /// Creates a new surface from the given drm configuration.
+    ///
+    /// # Safety
+    ///
+    /// - All parameters must point to valid DRM values.
+    ///
+    /// # Platform Support
+    ///
+    /// This function is only available on Unix-like platforms (Linux, FreeBSD) and
+    /// currently only works with the Vulkan backend.
     pub unsafe fn instance_create_surface_from_drm(
         &self,
         fd: i32,

wgpu-hal/src/vulkan/drm.rs

@@ -4,7 +4,12 @@ use std::{string::ToString, vec::Vec};
 use ash::{ext, khr, vk};
 
 impl super::Instance {
-    pub fn create_surface_from_drm(
+    /// Creates a new surface from the given drm configuration.
+    ///
+    /// # Safety
+    ///
+    /// - All parameters must point to valid DRM values.
+    pub unsafe fn create_surface_from_drm(
         &self,
         fd: i32,
         plane: u32,

wgpu-hal/src/vulkan/mod.rs

@@ -30,10 +30,12 @@ mod adapter;
 mod command;
 mod conv;
 mod device;
-mod drm;
 mod instance;
 mod sampler;
 
+#[cfg(all(unix, not(target_os = "macos")))]
+mod drm;
+
 use std::{
     borrow::Borrow,
     boxed::Box,

wgpu/src/api/surface.rs

@@ -299,6 +299,7 @@ pub enum SurfaceTargetUnsafe {
     ///
     /// - All parameters must point to valid DRM values and remain valid for as long as the resulting [`Surface`] exists.
     /// - The file descriptor (`fd`), plane, connector, and mode configuration must be valid and compatible.
+    #[cfg(all(unix, not(target_os = "macos")))]
     Drm {
         /// The file descriptor of the DRM device.
         fd: i32,

wgpu/src/backend/wgpu_core.rs

@@ -794,6 +794,7 @@ impl dispatch::InstanceInterface for ContextWgpuCore {
                     .instance_create_surface(raw_display_handle, raw_window_handle, None)
             },
 
+            #[cfg(all(unix, not(target_os = "macos")))]
             SurfaceTargetUnsafe::Drm {
                 fd,
                 plane,