2 files changed, 109 insertions, 0 deletions
diff --git a/gpu_buffer/src/lib.rs b/gpu_buffer/src/lib.rs
index 6d0cfa9..fb69eeb 100644
--- a/gpu_buffer/src/lib.rs
+++ b/gpu_buffer/src/lib.rs
@@ -31,7 +31,10 @@
 //! ```
 
 extern crate data_model;
+#[macro_use]
+extern crate sys_util;
 
+pub mod rendernode;
 mod raw;
 
 use std::os::raw::c_void;
diff --git a/gpu_buffer/src/rendernode.rs b/gpu_buffer/src/rendernode.rs
new file mode 100644
index 0000000..ce89a15
--- /dev/null
+++ b/gpu_buffer/src/rendernode.rs
@@ -0,0 +1,106 @@
+// Copyright 2018 The Chromium OS Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+use std::ffi::CString;
+use std::fs::{File, OpenOptions};
+use std::os::raw::{c_char, c_int, c_uint, c_ulonglong};
+use std::path::Path;
+use std::ptr::null_mut;
+
+use sys_util::ioctl_with_mut_ref;
+
+const DRM_IOCTL_BASE: c_uint = 0x64;
+
+#[repr(C)]
+#[derive(Copy, Clone)]
+struct drm_version {
+    version_major: c_int,
+    version_minor: c_int,
+    version_patchlevel: c_int,
+    name_len: c_ulonglong,
+    name: *mut c_char,
+    date_len: c_ulonglong,
+    date: *mut c_char,
+    desc_len: c_ulonglong,
+    desc: *mut c_char,
+}
+
+ioctl_iowr_nr!(DRM_IOCTL_VERSION, DRM_IOCTL_BASE, 0x0, drm_version);
+
+fn get_drm_device_name(fd: &File) -> Result<String, ()> {
+    let mut version = drm_version {
+        version_major: 0,
+        version_minor: 0,
+        version_patchlevel: 0,
+        name_len: 0,
+        name: null_mut(),
+        date_len: 0,
+        date: null_mut(),
+        desc_len: 0,
+        desc: null_mut(),
+    };
+
+    // Get the length of the device name.
+    if unsafe { ioctl_with_mut_ref(fd, DRM_IOCTL_VERSION(), &mut version) } < 0 {
+        return Err(());
+    }
+
+    // Enough bytes to hold the device name and terminating null character.
+    let mut name_bytes: Vec<u8> = vec![0; (version.name_len + 1) as usize];
+    let mut version = drm_version {
+        version_major: 0,
+        version_minor: 0,
+        version_patchlevel: 0,
+        name_len: name_bytes.len() as c_ulonglong,
+        name: name_bytes.as_mut_ptr() as *mut c_char,
+        date_len: 0,
+        date: null_mut(),
+        desc_len: 0,
+        desc: null_mut(),
+    };
+
+    // Safe as no more than name_len + 1 bytes will be written to name.
+    if unsafe { ioctl_with_mut_ref(fd, DRM_IOCTL_VERSION(), &mut version) } < 0 {
+        return Err(());
+    }
+
+    Ok(CString::new(&name_bytes[..(version.name_len as usize)])
+       .map_err(|_| ())?
+       .into_string().map_err(|_| ())?)
+}
+
+
+/// Returns a `fd` for an opened rendernode device, while filtering out specified
+/// undesired drivers.
+pub fn open_device(undesired: &[&str]) -> Result<File, ()> {
+    const DRM_DIR_NAME: &str = "/dev/dri";
+    const DRM_MAX_MINOR: u32 = 15;
+    const RENDER_NODE_START: u32 = 128;
+
+    for n in RENDER_NODE_START..(RENDER_NODE_START + DRM_MAX_MINOR + 1) {
+        let path = Path::new(DRM_DIR_NAME).join(format!("renderD{}", n));
+
+        if let Ok(fd) = OpenOptions::new().read(true).write(true).open(path) {
+            if let Ok(name) = get_drm_device_name(&fd) {
+                if !undesired.iter().any(|item| *item == name) {
+                    return Ok(fd);
+                }
+            }
+        }
+    }
+
+    Err(())
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    #[ignore] // no access to /dev/dri
+    fn open_rendernode_device() {
+        let undesired: &[&str] = &["bad_driver", "another_bad_driver"];
+        open_device(undesired).expect("failed to open rendernode");
+    }
+}