[PATCH][libdrm] drm: Fix multi GPU drmGetDevice return wrong device

[Qiang.Yu@xxxxxxx (Qiang Yu)]

drmGetDevice will always return the first device it find
under /dev/dri/. This is not true for multi GPU situation.

Plus fix the memory leak in error handling path of
drmGetDevices.

Change-Id: I2a85a8a4feba8a5cc517ad75c6afb532fa07c53d
Signed-off-by: Qiang Yu <Qiang.Yu at amd.com>
---
 xf86drm.c | 26 +++++++++++++++++++++-----
 1 file changed, 21 insertions(+), 5 deletions(-)

diff --git a/xf86drm.c b/xf86drm.c
index 6689f7c..e90e8e5 100644
--- a/xf86drm.c
+++ b/xf86drm.c
@@ -3064,6 +3064,17 @@ static void drmFoldDuplicatedDevices(drmDevicePtr local_devices[], int count)
             }
         }
     }
+
+    // move all devices to the beginning of local_devices continuously
+    for (i = 0, j = 0; i < count; i++) {
+        if (local_devices[i]) {
+            if (i != j) {
+                local_devices[j] = local_devices[i];
+                local_devices[i] = NULL;
+            }
+            j++;
+        }
+    }
 }
 
 /**
@@ -3087,6 +3098,7 @@ int drmGetDevice(int fd, drmDevicePtr *device)
     int maj, min;
     int ret, i, node_count;
     int max_count = 16;
+    dev_t find_rdev;
 
     if (fd == -1 || device == NULL)
         return -EINVAL;
@@ -3094,6 +3106,7 @@ int drmGetDevice(int fd, drmDevicePtr *device)
     if (fstat(fd, &sbuf))
         return -errno;
 
+    find_rdev = sbuf.st_rdev;
     maj = major(sbuf.st_rdev);
     min = minor(sbuf.st_rdev);
 
@@ -3154,7 +3167,13 @@ int drmGetDevice(int fd, drmDevicePtr *device)
             local_devices = temp;
         }
 
-        local_devices[i] = d;
+        /* move target to the first of local_devices */
+        if (find_rdev == sbuf.st_rdev && i) {
+            local_devices[i] = local_devices[0];
+            local_devices[0] = d;
+        }
+        else
+            local_devices[i] = d;
         i++;
     }
     node_count = i;
@@ -3267,10 +3286,7 @@ int drmGetDevices(drmDevicePtr devices[], int max_devices)
     drmFoldDuplicatedDevices(local_devices, node_count);
 
     device_count = 0;
-    for (i = 0; i < node_count; i++) {
-        if (!local_devices[i])
-            continue;
-
+    for (i = 0; i < node_count && local_devices[i]; i++) {
         if ((devices != NULL) && (device_count < max_devices))
             devices[device_count] = local_devices[i];
         else
-- 
1.9.1