[PATCH libdrm] libdrm: Fix issue about differrent domainID but same BDF

[Emily Deng]

For multiple GPUs which has the same BDF, but has different domain ID,
the drmOpenByBusid will return the wrong fd when startx.

The reproduce sequence as below:
1. Call drmOpenByBusid to open Card0, then will return the right fd0, and the
fd0 is master privilege;
2. Call drmOpenByBusid to open Card1. In function drmOpenByBusid, it will
open Card0 first, this time, the fd1 for opening Card0 is not master
privilege, and will call drmSetInterfaceVersion to identify the
domain ID feature, as the fd1 is not master privilege, then drmSetInterfaceVersion
will fail, and then won't compare domain ID, then return the wrong fd for Card1.

Solution:
First loop search the best match fd about drm 1.4.

Signed-off-by: Emily Deng <Emily.Deng at amd.com>
---
 xf86drm.c | 23 +++++++++++++++++++++++
 1 file changed, 23 insertions(+)

diff --git a/xf86drm.c b/xf86drm.c
index 336d64d..b60e029 100644
--- a/xf86drm.c
+++ b/xf86drm.c
@@ -584,11 +584,34 @@ static int drmOpenByBusid(const char *busid, int type)
     if (base < 0)
         return -1;
 
+    /* We need to try for 1.4 first for proper PCI domain support */
     drmMsg("drmOpenByBusid: Searching for BusID %s\n", busid);
     for (i = base; i < base + DRM_MAX_MINOR; i++) {
         fd = drmOpenMinor(i, 1, type);
         drmMsg("drmOpenByBusid: drmOpenMinor returns %d\n", fd);
         if (fd >= 0) {
+            sv.drm_di_major = 1;
+            sv.drm_di_minor = 4;
+            sv.drm_dd_major = -1;        /* Don't care */
+            sv.drm_dd_minor = -1;        /* Don't care */
+            if (!drmSetInterfaceVersion(fd, &sv)) {
+                buf = drmGetBusid(fd);
+                drmMsg("drmOpenByBusid: drmGetBusid reports %s\n", buf);
+                if (buf && drmMatchBusID(buf, busid, 1)) {
+                    drmFreeBusid(buf);
+                    return fd;
+                }
+                if (buf)
+                    drmFreeBusid(buf);
+            }
+            close(fd);
+        }
+    }
+
+   for (i = base; i < base + DRM_MAX_MINOR; i++) {
+        fd = drmOpenMinor(i, 1, type);
+        drmMsg("drmOpenByBusid: drmOpenMinor returns %d\n", fd);
+        if (fd >= 0) {
             /* We need to try for 1.4 first for proper PCI domain support
              * and if that fails, we know the kernel is busted
              */
-- 
2.7.4