gbm: Search LIBGL_DRIVERS_PATH if GBM_DRIVERS_PATH is not set

The GBM_DRIVERS_PATH environment variable is not documented, and only
used to set the location of gbm drivers, while LIBGL_DRIVERS_PATH is
used for everything else, and is documented.

Generally this split leads to confusion as to why gbm doesn't work.

This patch will read LIBGL_DRIVERS_PATH as a fallback if
GBM_DRIVERS_PATH is not set.

The comments clearly indicate that using LIBGL_DRIVERS_PATH is
preferred over GBM_DRIVERS_PATH.

v2: - Use GBM_DRIVERS_PATH as a fallback
v3: [jordan.l.justen@intel.com] - Make LIBGL_DRIVERS_PATH the fallback

Signed-off-by: Dylan Baker <baker.dylan.c@gmail.com>
Reviewed-by: Jordan Justen <jordan.l.justen@intel.com>
Reviewed-by: Kristian Høgsberg <krh@bitplanet.net>

1 files changed, 11 insertions, 1 deletions

diff --git a/src/gbm/backends/dri/gbm_dri.c b/src/gbm/backends/dri/gbm_dri.c
index 347bc99..47e62f3 100644
--- a/src/gbm/backends/dri/gbm_dri.c
+++ b/src/gbm/backends/dri/gbm_dri.c
@@ -211,9 +211,19 @@ dri_load_driver(struct gbm_dri_device *dri)
    char *get_extensions_name;
 
    search_paths = NULL;
+   /* don't allow setuid apps to use LIBGL_DRIVERS_PATH or GBM_DRIVERS_PATH */
    if (geteuid() == getuid()) {
-      /* don't allow setuid apps to use GBM_DRIVERS_PATH */
+      /* Read GBM_DRIVERS_PATH first for compatibility, but LIBGL_DRIVERS_PATH
+       * is recommended over GBM_DRIVERS_PATH.
+       */
       search_paths = getenv("GBM_DRIVERS_PATH");
+
+      /* Read LIBGL_DRIVERS_PATH if GBM_DRIVERS_PATH was not set.
+       * LIBGL_DRIVERS_PATH is recommended over GBM_DRIVERS_PATH.
+       */
+      if (search_paths == NULL) {
+         search_paths = getenv("LIBGL_DRIVERS_PATH");
+      }
    }
    if (search_paths == NULL)
       search_paths = DEFAULT_DRIVER_DIR;