lib/igt_device: Introduce igt_device_get_card_index

And use it! But let's start small.
Rather than going with "and by the way, here's the card index" from
igt_sysfs_path, we're making things more explicit.

v2: Drop idx comment. (Chris)

Signed-off-by: Michał Winiarski <michal.winiarski@intel.com>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>

1 files changed, 19 insertions, 0 deletions

diff --git a/lib/igt_device.c b/lib/igt_device.c
index 5b3722c8..08f39c8b 100644
--- a/lib/igt_device.c
+++ b/lib/igt_device.c
@@ -22,6 +22,8 @@
  *
  */
 
+#include <sys/stat.h>
+#include <sys/sysmacros.h>
 #include "igt.h"
 #include "igt_device.h"
 
@@ -84,3 +86,20 @@ void igt_device_drop_master(int fd)
 			      "Failed to drop DRM master.\n");
 	}
 }
+
+/**
+ * igt_device_get_card_index:
+ * @fd: the device
+ *
+ * Returns:
+ * Index (N) of /dev/dri/cardN or /dev/dri/renderDN corresponding with fd.
+ *
+ */
+int igt_device_get_card_index(int fd)
+{
+	struct stat st;
+
+	igt_fail_on(fstat(fd, &st) || !S_ISCHR(st.st_mode));
+
+	return minor(st.st_rdev);
+}