From 28320833d61af76dc3b77b985c69706f3e021836 Mon Sep 17 00:00:00 2001
From: Adam Jackson <ajax@redhat.com>
Date: Tue, 18 Sep 2018 14:37:51 -0400
Subject: [PATCH xserver] linux: Make platform device probe less fragile

At the point where xf86BusProbe runs we haven't yet taken our own VT,
which means we can't perform drm "master" operations on the device. This
is tragic, because we need master to fish the bus id string out of the
kernel, which we can only do after drmSetInterfaceVersion, which for
some reason stores that string on the device not the file handle and
thus needs master access.

Fortunately we know the format of the busid string, and it happens to
almost be the same as the ID_PATH variable from udev. Use that instead
and stop calling drmSetInterfaceVersion.

Signed-off-by: Adam Jackson <ajax@redhat.com>
---
 config/udev.c                              | 17 ++++++++++++-----
 hw/xfree86/os-support/linux/lnx_platform.c | 13 ++-----------
 2 files changed, 14 insertions(+), 16 deletions(-)

diff --git a/config/udev.c b/config/udev.c
index 3a73189e25..8c6c4b6665 100644
--- a/config/udev.c
+++ b/config/udev.c
@@ -56,7 +56,7 @@ static struct udev_monitor *udev_monitor;
 
 #ifdef CONFIG_UDEV_KMS
 static void
-config_udev_odev_setup_attribs(const char *path, const char *syspath,
+config_udev_odev_setup_attribs(struct udev_device *udev_device, const char *path, const char *syspath,
                                int major, int minor,
                                config_odev_probe_proc_ptr probe_callback);
 #endif
@@ -128,7 +128,7 @@ device_added(struct udev_device *udev_device)
 
         LogMessage(X_INFO, "config/udev: Adding drm device (%s)\n", path);
 
-        config_udev_odev_setup_attribs(path, syspath, major(devnum),
+        config_udev_odev_setup_attribs(udev_device, path, syspath, major(devnum),
                                        minor(devnum), NewGPUDeviceRequest);
         return;
     }
@@ -322,7 +322,7 @@ device_removed(struct udev_device *device)
 
         LogMessage(X_INFO, "config/udev: removing GPU device %s %s\n",
                    syspath, path);
-        config_udev_odev_setup_attribs(path, syspath, major(devnum),
+        config_udev_odev_setup_attribs(device, path, syspath, major(devnum),
                                        minor(devnum), DeleteGPUDeviceRequest);
         /* Retry vtenter after a drm node removal */
         systemd_logind_vtenter();
@@ -465,17 +465,24 @@ config_udev_fini(void)
 #ifdef CONFIG_UDEV_KMS
 
 static void
-config_udev_odev_setup_attribs(const char *path, const char *syspath,
+config_udev_odev_setup_attribs(struct udev_device *udev_device, const char *path, const char *syspath,
                                int major, int minor,
                                config_odev_probe_proc_ptr probe_callback)
 {
     struct OdevAttributes *attribs = config_odev_allocate_attributes();
+    const char *value;
 
     attribs->path = XNFstrdup(path);
     attribs->syspath = XNFstrdup(syspath);
     attribs->major = major;
     attribs->minor = minor;
 
+    value = udev_device_get_property_value(udev_device, "ID_PATH");
+    if (value && !strncmp(value, "pci-", 4)) {
+        attribs->busid = XNFstrdup(value);
+        attribs->busid[3] = ':';
+    }
+
     /* ownership of attribs is passed to probe layer */
     probe_callback(attribs);
 }
@@ -516,7 +523,7 @@ config_udev_odev_probe(config_odev_probe_proc_ptr probe_callback)
         else if (!check_seat(udev_device))
             goto no_probe;
 
-        config_udev_odev_setup_attribs(path, syspath, major(devnum),
+        config_udev_odev_setup_attribs(udev_device, path, syspath, major(devnum),
                                        minor(devnum), probe_callback);
     no_probe:
         udev_device_unref(udev_device);
diff --git a/hw/xfree86/os-support/linux/lnx_platform.c b/hw/xfree86/os-support/linux/lnx_platform.c
index 70374ace88..0eb6d22875 100644
--- a/hw/xfree86/os-support/linux/lnx_platform.c
+++ b/hw/xfree86/os-support/linux/lnx_platform.c
@@ -30,6 +30,8 @@ get_drm_info(struct OdevAttributes *attribs, char *path, int delayed_index)
     int err = 0;
     Bool paused, server_fd = FALSE;
 
+    LogMessage(X_INFO, "Platform probe for %s\n", attribs->syspath);
+
     fd = systemd_logind_take_fd(attribs->major, attribs->minor, path, &paused);
     if (fd != -1) {
         if (paused) {
@@ -53,13 +55,6 @@ get_drm_info(struct OdevAttributes *attribs, char *path, int delayed_index)
     sv.drm_dd_major = -1;       /* Don't care */
     sv.drm_dd_minor = -1;       /* Don't care */
 
-    err = drmSetInterfaceVersion(fd, &sv);
-    if (err) {
-        xf86Msg(X_ERROR, "%s: failed to set DRM interface version 1.4: %s\n",
-                path, strerror(-err));
-        goto out;
-    }
-
     /* for a delayed probe we've already added the device */
     if (delayed_index == -1) {
             xf86_add_platform_device(attribs, FALSE);
@@ -69,10 +64,6 @@ get_drm_info(struct OdevAttributes *attribs, char *path, int delayed_index)
     if (server_fd)
         xf86_platform_devices[delayed_index].flags |= XF86_PDEV_SERVER_FD;
 
-    buf = drmGetBusid(fd);
-    xf86_platform_odev_attributes(delayed_index)->busid = XNFstrdup(buf);
-    drmFreeBusid(buf);
-
     v = drmGetVersion(fd);
     if (!v) {
         xf86Msg(X_ERROR, "%s: failed to query DRM version\n", path);
-- 
2.19.0