[PATCH RFC 4/4] samples: rust: Add sample demonstrating DRM buddy allocator

Joel Fernandes
2025-10-30T19:06:40Z

Demonstrates usage of the DRM buddy allocator bindings through
a simple test module that initializes the allocator, performs
allocations, and prints information about the allocated blocks.

Signed-off-by: Joel Fernandes <joelagnelf@nvidia.com>
---
samples/rust/Kconfig | 14 +++++
samples/rust/Makefile | 1 +
samples/rust/rust_drm_buddy.rs | 106 +++++++++++++++++++++++++++++++++
3 files changed, 121 insertions(+)
create mode 100644 samples/rust/rust_drm_buddy.rs

diff --git a/samples/rust/Kconfig b/samples/rust/Kconfig
index b45631e2593c..8ccb4064ba91 100644
--- a/samples/rust/Kconfig
+++ b/samples/rust/Kconfig
@@ -21,6 +21,20 @@ config SAMPLE_RUST_CLIST

If unsure, say N.

+config SAMPLE_RUST_DRM_BUDDY
+ tristate "DRM buddy allocator sample"
+ depends on DRM_BUDDY
+ help
+ This option builds the Rust DRM buddy allocator sample.
+
+ The sample demonstrates using the DRM buddy allocator bindings
+ to allocate and free memory blocks.
+
+ To compile this as a module, choose M here:
+ the module will be called rust_drm_buddy.
+
+ If unsure, say N.
+
config SAMPLE_RUST_CONFIGFS
tristate "Configfs sample"
depends on CONFIGFS_FS
diff --git a/samples/rust/Makefile b/samples/rust/Makefile
index f8899c0df762..a56204ee4e96 100644
--- a/samples/rust/Makefile
+++ b/samples/rust/Makefile
@@ -2,6 +2,7 @@
ccflags-y += -I$(src) # needed for trace events

obj-$(CONFIG_SAMPLE_RUST_CLIST) += rust_clist.o
+obj-$(CONFIG_SAMPLE_RUST_DRM_BUDDY) += rust_drm_buddy.o
obj-$(CONFIG_SAMPLE_RUST_MINIMAL) += rust_minimal.o
obj-$(CONFIG_SAMPLE_RUST_MISC_DEVICE) += rust_misc_device.o
obj-$(CONFIG_SAMPLE_RUST_PRINT) += rust_print.o
diff --git a/samples/rust/rust_drm_buddy.rs b/samples/rust/rust_drm_buddy.rs
new file mode 100644
index 000000000000..96907bc19243
--- /dev/null
+++ b/samples/rust/rust_drm_buddy.rs
@@ -0,0 +1,106 @@
+// SPDX-License-Identifier: GPL-2.0
+
+//! Rust DRM buddy allocator sample.
+//!
+//! This sample demonstrates using the DRM buddy allocator from Rust.
+
+use kernel::{
+ drm::buddy::{
+ BuddyFlags,
+ DrmBuddy, //
+ },
+ prelude::*,
+ sizes::*, //
+};
+
+module! {
+ type: RustDrmBuddySample,
+ name: "rust_drm_buddy",
+ authors: ["Joel Fernandes"],
+ description: "DRM buddy allocator sample",
+ license: "GPL",
+}
+
+struct RustDrmBuddySample;
+
+impl kernel::Module for RustDrmBuddySample {
+ fn init(_module: &'static ThisModule) -> Result<Self> {
+ // Create a buddy allocator managing 1GB with 4KB chunks.
+ let buddy = DrmBuddy::new(SZ_1G, SZ_4K)?;
+
+ pr_info!("=== Test 1: Single 16MB block ===\n");
+ let allocated = buddy.alloc_blocks(
+ 0,
+ 0,
+ SZ_16M,
+ SZ_4K,
+ BuddyFlags::RANGE_ALLOCATION,
+ GFP_KERNEL,
+ )?;
+
+ let mut count = 0;
+ for block in &allocated {
+ pr_info!(
+ " Block {}: offset=0x{:x}, order={}, size={}\n",
+ count,
+ block.offset(),
+ block.order(),
+ block.size(&buddy)
+ );
+ count += 1;
+ }
+ pr_info!(" Total: {} blocks\n", count);
+ drop(allocated);
+
+ pr_info!("=== Test 2: Three 4MB blocks ===\n");
+ let allocated = buddy.alloc_blocks(
+ 0,
+ 0,
+ SZ_4M * 3,
+ SZ_4K,
+ BuddyFlags::RANGE_ALLOCATION,
+ GFP_KERNEL,
+ )?;
+
+ count = 0;
+ for block in &allocated {
+ pr_info!(
+ " Block {}: offset=0x{:x}, order={}, size={}\n",
+ count,
+ block.offset(),
+ block.order(),
+ block.size(&buddy)
+ );
+ count += 1;
+ }
+ pr_info!(" Total: {} blocks\n", count);
+ drop(allocated);
+
+ pr_info!("=== Test 3: Two 8MB blocks ===\n");
+ let allocated = buddy.alloc_blocks(
+ 0,
+ 0,
+ SZ_8M * 2,
+ SZ_4K,
+ BuddyFlags::RANGE_ALLOCATION,
+ GFP_KERNEL,
+ )?;
+
+ count = 0;
+ for block in &allocated {
+ pr_info!(
+ " Block {}: offset=0x{:x}, order={}, size={}\n",
+ count,
+ block.offset(),
+ block.order(),
+ block.size(&buddy)
+ );
+ count += 1;
+ }
+ pr_info!(" Total: {} blocks\n", count);
+
+ pr_info!("=== All tests passed! ===\n");
+
+ Ok(RustDrmBuddySample {})
+ }
+}
--
2.34.1