Feat: start experimental primary context stuff

Author: RDambrosio016

crates/cust/src/lib.rs

@@ -66,6 +66,7 @@ pub mod link;
 pub mod memory;
 pub mod module;
 pub mod prelude;
+pub mod primary;
 pub mod stream;
 // WIP
 mod surface;

crates/cust/src/primary.rs

@@ -0,0 +1,64 @@
+use crate::{
+    context::ContextFlags,
+    device::Device,
+    error::{CudaResult, ToResult},
+    sys as cuda,
+};
+use std::mem::MaybeUninit;
+
+#[derive(Debug)]
+pub struct Context {
+    inner: cuda::CUcontext,
+    device: cuda::CUdevice,
+}
+
+impl Context {
+    /// Retains the primary context for this device, incrementing the internal reference cycle
+    /// that CUDA keeps track of. There is only one primary context associated with a device, multiple
+    /// calls to this function with the same device will return the same internal context.
+    ///
+    /// This will **NOT** push the context to the stack, primary contexts do not interoperate
+    /// with the context stack.
+    pub fn new(device: &Device) -> CudaResult<Self> {
+        let mut inner = MaybeUninit::uninit();
+        unsafe {
+            cuda::cuDevicePrimaryCtxRetain(inner.as_mut_ptr(), device.as_raw()).to_result()?;
+            Ok(Self {
+                inner: inner.assume_init(),
+                device: device.as_raw(),
+            })
+        }
+    }
+
+    /// Resets the primary context associated with the device, freeing all allocations created
+    /// inside of the context. You must make sure that nothing else is using the context or using
+    /// CUDA on the device in general. For this reason, it is usually highly advised to not use
+    /// this function.
+    ///
+    /// # Safety
+    ///
+    /// Nothing else should be using the primary context for this device, otherwise,
+    /// spurious errors or segfaults will occur.
+    pub unsafe fn reset(device: &Device) -> CudaResult<()> {
+        cuda::cuDevicePrimaryCtxReset_v2(device.as_raw()).to_result()
+    }
+
+    /// Sets the flags for the device context, these flags will apply to any user of the primary
+    /// context associated with this device.
+    pub fn set_flags(&self, flags: ContextFlags) -> CudaResult<()> {
+        unsafe { cuda::cuDevicePrimaryCtxSetFlags_v2(self.device, flags.bits()).to_result() }
+    }
+
+    /// Returns the raw handle to this context.
+    pub fn as_raw(&self) -> cuda::CUcontext {
+        self.inner
+    }
+}
+
+impl Drop for Context {
+    fn drop(&mut self) {
+        unsafe {
+            cuda::cuDevicePrimaryCtxRelease_v2(self.device);
+        }
+    }
+}