x11: Workaround nvidia driver lacking DRI

wgpu/Cargo.toml

@@ -53,4 +53,4 @@ wayland-client = { version = "0.31.2" }
 wayland-sys = { version = "0.31.1", features = ["dlopen"] }
 as-raw-xcb-connection = "1.0.1"
 tiny-xlib = "0.2.3"
-x11rb = { version = "0.13.1", features = ["allow-unsafe-code", "dl-libxcb", "dri3"] }
+x11rb = { version = "0.13.1", features = ["allow-unsafe-code", "dl-libxcb", "dri3", "randr"] }

wgpu/src/window/x11.rs

@@ -1,14 +1,26 @@
+use std::{
+    fs,
+    io::{BufRead, BufReader},
+    path::Path,
+};
+
 use crate::graphics::compositor::Window;
 
 use as_raw_xcb_connection::AsRawXcbConnection;
 use raw_window_handle::{
     RawDisplayHandle, XcbDisplayHandle, XlibDisplayHandle,
 };
-use rustix::fs::fstat;
+use rustix::fs::{fstat, stat};
 use tiny_xlib::Display;
 use x11rb::{
     connection::{Connection, RequestConnection},
-    protocol::dri3::{ConnectionExt as _, X11_EXTENSION_NAME as DRI3_NAME},
+    protocol::{
+        dri3::{ConnectionExt as _, X11_EXTENSION_NAME as DRI3_NAME},
+        randr::{
+            ConnectionExt as _, ProviderCapability,
+            X11_EXTENSION_NAME as RANDR_NAME,
+        },
+    },
     xcb_ffi::XCBConnection,
 };
 
@@ -57,21 +69,103 @@ pub fn get_x11_device_ids<W: Window>(window: &W) -> Option<(u16, u16)> {
             return None;
         }
     };
+    let root = conn.setup().roots[screen as usize].root;
 
-    // check for DRI3
-    let _ = conn.extension_information(DRI3_NAME).ok()??;
-    // we have dri3, dri3_open exists on any version, so lets skip version checks.
+    // The nvidia xorg driver advertises DRI2 and DRI3,
+    // but doesn't really return any useful data for either of them.
+    // We also can't query EGL, as a display created from an X11 display
+    // running on the properietary driver won't return an EGLDevice.
+    //
+    // So we have to resort to hacks.
+
+    // check for randr
+    let _ = conn.extension_information(RANDR_NAME).ok()??;
+    // check version, because we need providers to exist
+    let version = conn.randr_query_version(1, 4).ok()?.reply().ok()?;
+    if version.major_version < 1
+        || (version.major_version == 1 && version.minor_version < 4)
+    {
+        return None;
+    }
+
+    // get the name of the first Source Output provider, that will be our main device
+    let randr = conn.randr_get_providers(root).ok()?.reply().ok()?;
+    let mut name = None;
+    for provider in randr.providers {
+        let info = conn
+            .randr_get_provider_info(provider, randr.timestamp)
+            .ok()?
+            .reply()
+            .ok()?;
+        if info
+            .capabilities
+            .contains(ProviderCapability::SOURCE_OUTPUT)
+            || name.is_none()
+        {
+            name = std::str::from_utf8(&info.name)
+                .ok()
+                .map(ToString::to_string);
+        }
+    }
+
+    // if that name is formatted `NVIDIA-x`, then x represents the /dev/nvidiaX number, which we can relate to /dev/dri
+    if let Some(number) = name.and_then(|name| {
+        name.trim().strip_prefix("NVIDIA-")?.parse::<u32>().ok()
+    }) {
+        // let it be known, that I hate this "interface"...
+        for busid in fs::read_dir("/proc/driver/nvidia/gpus")
+            .ok()?
+            .map(Result::ok)
+            .flatten()
+        {
+            for line in BufReader::new(
+                fs::File::open(busid.path().join("information")).ok()?,
+            )
+            .lines()
+            {
+                if let Ok(line) = line {
+                    if line.starts_with("Device Minor") {
+                        if let Some((_, num)) = line.split_once(":") {
+                            let minor = num.trim().parse::<u32>().ok()?;
+                            if minor == number {
+                                // we found the device
+                                for device in fs::read_dir(
+                                    Path::new("/sys/module/nvidia/drivers/pci:nvidia/")
+                                        .join(busid.file_name())
+                                        .join("drm"),
+                                )
+                                .ok()?
+                                .map(Result::ok)
+                                .flatten()
+                                {
+                                    let device = device.file_name();
+                                    if device.to_string_lossy().starts_with("card")
+                                        || device.to_string_lossy().starts_with("render")
+                                    {
+                                        let stat =
+                                            stat(Path::new("/dev/dri").join(device)).ok()?;
+                                        let dev = stat.st_rdev;
+                                        return super::ids_from_dev(dev);
+                                    }
+                                }
+                            }
+                        }
+                    }
+                }
+            }
+        }
 
-    // provider being NONE tells the X server to use the RandR provider.
-    let screen = &conn.setup().roots[screen as usize];
-    let dri3 = conn
-        .dri3_open(screen.root, x11rb::NONE)
-        .ok()?
-        .reply()
-        .ok()?;
-    let device_fd = dri3.device_fd;
-    let stat = fstat(device_fd).ok()?;
-    let dev = stat.st_rdev;
+        None
+    } else {
+        // check via DRI3
+        let _ = conn.extension_information(DRI3_NAME).ok()??;
+        // we have dri3, dri3_open exists on any version, so skip version checks.
 
-    super::ids_from_dev(dev)
+        // provider being NONE tells the X server to use the RandR provider.
+        let dri3 = conn.dri3_open(root, x11rb::NONE).ok()?.reply().ok()?;
+        let device_fd = dri3.device_fd;
+        let stat = fstat(device_fd).ok()?;
+        let dev = stat.st_rdev;
+        super::ids_from_dev(dev)
+    }
 }