loader: Factor out the common driver opening logic from each loader.

I copied the code from egl_dri2.c, but the functionality was equivalent
between all the loaders other than their particular environment variables.

v2: Drop the logging function equivalent to loader_default_logger()
    (requested by Eric, Emil).  Move the SCons workaround across.  Drop
    the now-unused driGetDriverExtensions() declaration that was lost in a
    rebase.

Reviewed-by: Eric Engestrom <[email protected]> (v1)
Reviewed-by: Emil Velikov <[email protected]> (v1)

1 files changed, 7 insertions, 0 deletions

diff --git a/src/loader/loader.h b/src/loader/loader.h
index 7b4dd01144f..779ec44b75d 100644
--- a/src/loader/loader.h
+++ b/src/loader/loader.h
@@ -33,6 +33,8 @@
 extern "C" {
 #endif
 
+struct __DRIextensionRec;
+
 /* Helpers to figure out driver and device name, eg. from pci-id, etc. */
 
 int
@@ -47,6 +49,11 @@ loader_get_pci_id_for_fd(int fd, int *vendor_id, int *chip_id);
 char *
 loader_get_driver_for_fd(int fd);
 
+const struct __DRIextensionRec **
+loader_open_driver(const char *driver_name,
+                   void **out_driver_handle,
+                   const char **search_path_vars);
+
 char *
 loader_get_device_name_for_fd(int fd);