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>

1 files changed, 12 insertions, 4 deletions

diff --git a/xf86drm.c b/xf86drm.c
index b5eeeb09..f6850aa2 100644
--- a/xf86drm.c
+++ b/xf86drm.c
@@ -2838,7 +2838,7 @@ out_close_dir:
     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 @@ out_close_dir:
         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 @@ int drmGetDevice2(int fd, uint32_t flags, drmDevicePtr *device)
     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 @@ int drmGetDevice2(int fd, uint32_t flags, drmDevicePtr *device)
         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))