backend: add preliminary support for driver detection

Signed-off-by: Yuxuan Shui <yshuiv7@gmail.com>

src/backend/backend.h

@@ -5,6 +5,7 @@
 
 #include <stdbool.h>
 
+#include "driver.h"
 #include "compiler.h"
 #include "kernel.h"
 #include "region.h"
@@ -176,6 +177,9 @@ struct backend_operations {
 
 	// ===========         Hooks        ============
 	/// Let the backend hook into the event handling queue
+	// ===========         Misc         ============
+	/// Return the driver that is been used by the backend
+	enum driver (*detect_driver)(backend_t *backend_data);
 };
 
 typedef backend_t *(*backend_init_fn)(session_t *ps)attr_nonnull(1);

src/backend/driver.c

@@ -0,0 +1,62 @@
+// SPDX-License-Identifier: MPL-2.0
+// Copyright (c) Yuxuan Shui <yshuiv7@gmail.com>
+
+#include <xcb/randr.h>
+#include <xcb/xcb.h>
+
+#include "backend/backend.h"
+#include "backend/driver.h"
+#include "common.h"
+
+enum driver detect_driver(xcb_connection_t *c, backend_t *backend_data, xcb_window_t window) {
+	enum driver ret = 0;
+	// First we try doing backend agnostic detection using RANDR
+	// There's no way to query the X server about what driver is loaded, so RANDR is
+	// our best shot.
+	auto randr_version = xcb_randr_query_version_reply(
+	    c, xcb_randr_query_version(c, XCB_RANDR_MAJOR_VERSION, XCB_RANDR_MINOR_VERSION),
+	    NULL);
+	if (randr_version &&
+	    (randr_version->major_version > 1 || randr_version->minor_version >= 4)) {
+		auto r = xcb_randr_get_providers_reply(
+		    c, xcb_randr_get_providers(c, window), NULL);
+		if (r == NULL) {
+			log_warn("Failed to get RANDR providers");
+			return 0;
+		}
+
+		auto providers = xcb_randr_get_providers_providers(r);
+		for (auto i = 0; i < xcb_randr_get_providers_providers_length(r); i++) {
+			auto r2 = xcb_randr_get_provider_info_reply(
+			    c, xcb_randr_get_provider_info(c, providers[i], r->timestamp), NULL);
+			if (r2 == NULL) {
+				continue;
+			}
+			if (r2->num_outputs == 0) {
+				free(r2);
+				continue;
+			}
+
+			auto name = xcb_randr_get_provider_info_name(r2);
+			if (strcasestr(name, "modesetting") != NULL) {
+				ret |= DRIVER_MODESETTING;
+			} else if (strcasestr(name, "Radeon") != NULL) {
+				// Be conservative, add both radeon drivers
+				ret |= DRIVER_AMDGPU | DRIVER_RADEON;
+			} else if (strcasestr(name, "NVIDIA") != NULL) {
+				ret |= DRIVER_NVIDIA;
+			} else if (strcasestr(name, "nouveau") != NULL) {
+				ret |= DRIVER_NOUVEAU;
+			} else if (strcasestr(name, "Intel") != NULL) {
+				ret |= DRIVER_INTEL;
+			}
+		}
+		free(r);
+	}
+
+	// If the backend supports driver detection, use that as well
+	if (backend_data && backend_data->ops->detect_driver) {
+		ret |= backend_data->ops->detect_driver(backend_data);
+	}
+	return ret;
+}

src/backend/driver.h

@@ -0,0 +1,55 @@
+// SPDX-License-Identifier: MPL-2.0
+// Copyright (c) Yuxuan Shui <yshuiv7@gmail.com>
+
+#pragma once
+
+#include <stdio.h>
+#include <xcb/xcb.h>
+
+struct session;
+struct backend_base;
+
+/// A list of possible drivers.
+/// The driver situation is a bit complicated. There are two drivers we care about: the
+/// DDX, and the OpenGL driver. They are usually paired, but not always, since there is
+/// also the generic modesetting driver.
+/// This enum represents _both_ drivers.
+enum driver {
+	DRIVER_AMDGPU = 1, // AMDGPU for DDX, radeonsi for OpenGL
+	DRIVER_RADEON = 2, // ATI for DDX, mesa r600 for OpenGL
+	DRIVER_FGLRX = 4,
+	DRIVER_NVIDIA = 8,
+	DRIVER_NOUVEAU = 16,
+	DRIVER_INTEL = 32,
+	DRIVER_MODESETTING = 64,
+};
+
+/// Return a list of drivers currently in use by the X server.
+/// Note, this is a best-effort test, so no guarantee all drivers will be detected.
+enum driver detect_driver(xcb_connection_t *, struct backend_base *, xcb_window_t);
+
+// Print driver names to stdout, for diagnostics
+static inline void print_drivers(enum driver drivers) {
+	if (drivers & DRIVER_AMDGPU) {
+		printf("AMDGPU, ");
+	}
+	if (drivers & DRIVER_RADEON) {
+		printf("Radeon, ");
+	}
+	if (drivers & DRIVER_FGLRX) {
+		printf("fglrx, ");
+	}
+	if (drivers & DRIVER_NVIDIA) {
+		printf("NVIDIA, ");
+	}
+	if (drivers & DRIVER_NOUVEAU) {
+		printf("nouveau, ");
+	}
+	if (drivers & DRIVER_INTEL) {
+		printf("Intel, ");
+	}
+	if (drivers & DRIVER_MODESETTING) {
+		printf("modesetting, ");
+	}
+	printf("\b\b \n");
+}

src/backend/meson.build

@@ -1,5 +1,5 @@
 # enable xrender
-srcs += [ files('backend_common.c', 'xrender/xrender.c', 'backend.c') ]
+srcs += [ files('backend_common.c', 'xrender/xrender.c', 'backend.c', 'driver.c') ]
 
 # enable opengl
 if get_option('opengl')