commit d5cf3f98314c1b9d87216e00c30c9fef06ff24c3
author Jonathan Gray <jsg@jsg.id.au> Sat Dec 17 16:09:51 2016 +1100
committer Emil Velikov <emil.l.velikov@gmail.com> Sat Dec 24 17:06:49 2016 +0000
tree 16479426affd410a56731ac1b99a61e4eb1809a6
parent e3af5368b2c372cfda27bc010b9c98a923d83cd9

xf86drm: adjust device node path for minor base

When constructing a path to a device node the minor number retrieved
from fstat needs to have the offset of the node type subtracted from it.
Control and render node types have the same major as the primary node
but each has their own block of minor types at fixed offsets.

v2: remove min < base test as requested by Emil

Reviewed-by: Emil Velikov <emil.l.velikov@gmail.com>
Signed-off-by: Jonathan Gray <jsg@jsg.id.au>

xf86drm.c

diff --git a/xf86drm.c b/xf86drm.c
index b5eeeb0..f6850aa 100644
--- a/xf86drm.c
+++ b/xf86drm.c
@@ -2838,7 +2838,7 @@
     char buf[PATH_MAX + 1];
     const char *dev_name;
     unsigned int maj, min;
-    int n;
+    int n, base;
 
     if (fstat(fd, &sbuf))
         return NULL;
@@ -2863,7 +2863,11 @@
         return NULL;
     };
 
-    n = snprintf(buf, sizeof(buf), dev_name, DRM_DIR_NAME, min);
+    base = drmGetMinorBase(type);
+    if (base < 0)
+        return NULL;
+
+    n = snprintf(buf, sizeof(buf), dev_name, DRM_DIR_NAME, min - base);
     if (n == -1 || n >= sizeof(buf))
         return NULL;
 
@@ -3262,7 +3266,7 @@
     char             node[PATH_MAX + 1];
     const char      *dev_name;
     int              node_type, subsystem_type;
-    int              maj, min, n, ret;
+    int              maj, min, n, ret, base;
 
     if (fd == -1 || device == NULL)
         return -EINVAL;
@@ -3294,7 +3298,11 @@
         return -EINVAL;
     };
 
-    n = snprintf(node, PATH_MAX, dev_name, DRM_DIR_NAME, min);
+    base = drmGetMinorBase(node_type);
+    if (base < 0)
+        return -EINVAL;
+
+    n = snprintf(node, PATH_MAX, dev_name, DRM_DIR_NAME, min - base);
     if (n == -1 || n >= PATH_MAX)
       return -errno;
     if (stat(node, &sbuf))