From 4ace478545af36d4df09d6ecdc6e56f606899ddd Mon Sep 17 00:00:00 2001
From: Dorinda Bassey <dbassey@redhat.com>
Date: Wed, 26 Nov 2025 14:01:38 +0100
Subject: [PATCH] util/rust: Add handle type detection to descriptor API

This enhances the DescriptorType enum to include the
memory handle type (DMABUF vs SHM) alongside the size,
allowing consumers to differentiate between DMA-BUF and
shared memory file descriptors without redundant code.

Signed-off-by: Dorinda Bassey <dbassey@redhat.com>
Reviewed-by: Gurchetan Singh <gurchetansingh@chromium.org>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/38677>
---
 src/util/rust/defines.rs              |  2 +-
 src/util/rust/sys/linux/descriptor.rs | 23 ++++++++++++++++++++++-
 2 files changed, 23 insertions(+), 2 deletions(-)

diff --git a/src/util/rust/defines.rs b/src/util/rust/defines.rs
index 207bc2bd1d2..ace3202d1ee 100644
--- a/src/util/rust/defines.rs
+++ b/src/util/rust/defines.rs
@@ -86,7 +86,7 @@ pub const WAIT_CONTEXT_MAX: usize = 16;
 
 pub enum DescriptorType {
     Unknown,
-    Memory(u32),
+    Memory(u32, u32), // (size, handle_type)
     WritePipe,
 }
 
diff --git a/src/util/rust/sys/linux/descriptor.rs b/src/util/rust/sys/linux/descriptor.rs
index 5c266bf17f0..8e50006ed56 100644
--- a/src/util/rust/sys/linux/descriptor.rs
+++ b/src/util/rust/sys/linux/descriptor.rs
@@ -1,6 +1,7 @@
 // Copyright 2025 Google
 // SPDX-License-Identifier: MIT
 
+use std::fs::read_link;
 use std::fs::File;
 use std::io::Error;
 use std::io::ErrorKind;
@@ -22,6 +23,8 @@ use crate::descriptor::AsRawDescriptor;
 use crate::descriptor::FromRawDescriptor;
 use crate::descriptor::IntoRawDescriptor;
 use crate::DescriptorType;
+use crate::MESA_HANDLE_TYPE_MEM_DMABUF;
+use crate::MESA_HANDLE_TYPE_MEM_SHM;
 
 pub type RawDescriptor = RawFd;
 pub const DEFAULT_RAW_DESCRIPTOR: RawDescriptor = -1;
@@ -43,7 +46,10 @@ impl OwnedDescriptor {
                 let size: u32 = seek_size
                     .try_into()
                     .map_err(|_| Error::from(ErrorKind::Unsupported))?;
-                Ok(DescriptorType::Memory(size))
+
+                let handle_type = self.get_memory_handle_type()?;
+
+                Ok(DescriptorType::Memory(size, handle_type))
             }
             _ => {
                 let flags = fcntl_getfl(&self.owned)?;
@@ -54,6 +60,21 @@ impl OwnedDescriptor {
             }
         }
     }
+
+    fn get_memory_handle_type(&self) -> Result<u32> {
+        let fd_path = read_link(format!("/proc/self/fd/{}", self.as_raw_descriptor()))
+            .map_err(|_| Error::from(ErrorKind::Unsupported))?;
+
+        let path_str = fd_path.to_string_lossy();
+        if path_str.starts_with("/dmabuf:") {
+            Ok(MESA_HANDLE_TYPE_MEM_DMABUF)
+        } else if path_str.starts_with("/memfd:") {
+            Ok(MESA_HANDLE_TYPE_MEM_SHM)
+        } else {
+            // Default to SHM for unknown types
+            Ok(MESA_HANDLE_TYPE_MEM_SHM)
+        }
+    }
 }
 
 impl AsRawDescriptor for OwnedDescriptor {