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>

4 files changed, 29 insertions, 6 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);
+}
diff --git a/lib/igt_device.h b/lib/igt_device.h
index 2995f969..9d7dc2c3 100644
--- a/lib/igt_device.h
+++ b/lib/igt_device.h
@@ -31,4 +31,6 @@ void igt_device_set_master(int fd);
 int __igt_device_drop_master(int fd);
 void igt_device_drop_master(int fd);
 
+int igt_device_get_card_index(int fd);
+
 #endif /* __IGT_DEVICE_H__ */
diff --git a/lib/igt_sysfs.c b/lib/igt_sysfs.c
index c57e4ae2..5a25d579 100644
--- a/lib/igt_sysfs.c
+++ b/lib/igt_sysfs.c
@@ -41,6 +41,7 @@
 
 #include "igt_core.h"
 #include "igt_sysfs.h"
+#include "igt_device.h"
 
 /**
  * SECTION:igt_sysfs
@@ -89,14 +90,13 @@ static int writeN(int fd, const char *buf, int len)
  * @device: fd of the device
  * @path: buffer to fill with the sysfs path to the device
  * @pathlen: length of @path buffer
- * @idx: optional pointer to store the card index of the opened device
  *
  * This finds the sysfs directory corresponding to @device.
  *
  * Returns:
  * The directory path, or NULL on failure.
  */
-char *igt_sysfs_path(int device, char *path, int pathlen, int *idx)
+char *igt_sysfs_path(int device, char *path, int pathlen)
 {
 	struct stat st;
 
@@ -125,8 +125,7 @@ char *igt_sysfs_path(int device, char *path, int pathlen, int *idx)
 			continue;
 
 		path[len] = '\0';
-		if (idx)
-			*idx = n;
+
 		return path;
 	}
 
@@ -148,9 +147,12 @@ int igt_sysfs_open(int device, int *idx)
 {
 	char path[80];
 
-	if (!igt_sysfs_path(device, path, sizeof(path), idx))
+	if (!igt_sysfs_path(device, path, sizeof(path)))
 		return -1;
 
+	if (idx)
+		*idx = igt_device_get_card_index(device);
+
 	return open(path, O_RDONLY);
 }
 
diff --git a/lib/igt_sysfs.h b/lib/igt_sysfs.h
index 2ce5b7bd..b181a95f 100644
--- a/lib/igt_sysfs.h
+++ b/lib/igt_sysfs.h
@@ -28,7 +28,7 @@
 #include <stdbool.h>
 #include <stdarg.h>
 
-char *igt_sysfs_path(int device, char *path, int pathlen, int *idx);
+char *igt_sysfs_path(int device, char *path, int pathlen);
 int igt_sysfs_open(int device, int *idx);
 int igt_sysfs_open_parameters(int device);
 bool igt_sysfs_set_parameter(int device,