[PATCH libdrm 1/3] xf86drm: adjust device node path for minor base

[Jonathan Gray]

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.

Signed-off-by: Jonathan Gray <jsg at jsg.id.au>
---
 xf86drm.c | 16 ++++++++++++----
 1 file changed, 12 insertions(+), 4 deletions(-)

diff --git a/xf86drm.c b/xf86drm.c
index 2e8c956..6705605 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 || min < base)
+        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 || min < base)
+        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))
-- 
2.10.2