[PATCH v9 1/4] lib/igt_sysfs: Add engine list helpers

[Jonathan Cavitt <jonathan.cavitt@intel.com>]

Create two new helper functions, igt_sysfs_get_engine_list and
igt_sysfs_free_engine_list, that create and destroy lists of open
engines, respectively.  The list created by igt_sysfs_get_engine_list
can be used to iterate over the set of engines in sysfs/engines and must
be freed by igt_sysfs_free_engine_list after use.

Signed-off-by: Jonathan Cavitt <jonathan.cavitt@intel.com>
---
 lib/igt_sysfs.c | 61 +++++++++++++++++++++++++++++++++++++++++++++++++
 lib/igt_sysfs.h |  3 +++
 2 files changed, 64 insertions(+)

diff --git a/lib/igt_sysfs.c b/lib/igt_sysfs.c
index 00d5822fd3..eaf8fd8829 100644
--- a/lib/igt_sysfs.c
+++ b/lib/igt_sysfs.c
@@ -1307,6 +1307,67 @@ static uint16_t xe_get_engine_class(char *name)
 	return class;
 }
 
+/**
+ * igt_sysfs_get_engine_list:
+ * @engines: fd of the directory engine
+ *
+ * Iterates over sysfs/engines and returns an array of
+ * opened engines.  The user will be in charge of closing
+ * the opened engines.
+ *
+ * The returned array will always be terminated by a -1.
+ */
+int *igt_sysfs_get_engine_list(int engines)
+{
+	struct dirent *de;
+	DIR *dir;
+	const int array_max = 16;
+	int *ret = calloc(array_max, sizeof(int));
+	int size = 0;
+
+	igt_assert(ret);
+
+	lseek(engines, 0, SEEK_SET);
+
+	dir = fdopendir(engines);
+	if (!dir)
+		close(engines);
+
+	while ((de = readdir(dir))) {
+		if (*de->d_name == '.')
+			continue;
+		igt_assert_lt(size, array_max);
+		ret[size] = openat(engines, de->d_name, O_RDONLY);
+		if (ret[size] < 0) {
+			ret[size] = 0;
+			continue;
+		}
+		size += 1;
+	}
+
+	igt_assert_lt(size, array_max);
+	ret[size] = -1;
+
+	return ret;
+}
+
+/**
+ * igt_sysfs_free_engine_list:
+ * @list: list of opened engines
+ * @size: number of engines in list
+ *
+ * Helper for cleaning up after igt_sysfs_get_engine_list.
+ * Closes all engines in list before freeing the list.
+ */
+void igt_sysfs_free_engine_list(int *list)
+{
+	int i = 0;
+
+	while (list[i] != -1)
+		close(list[i++]);
+	free(list);
+}
+
 /**
  * igt_sysfs_engines:
  * @xe: fd of the device
diff --git a/lib/igt_sysfs.h b/lib/igt_sysfs.h
index 54a4087918..86345f3d1b 100644
--- a/lib/igt_sysfs.h
+++ b/lib/igt_sysfs.h
@@ -168,6 +168,9 @@ typedef struct igt_sysfs_rw_attr {
 
 void igt_sysfs_rw_attr_verify(igt_sysfs_rw_attr_t *rw);
 
+int *igt_sysfs_get_engine_list(int engines);
+void igt_sysfs_free_engine_list(int *list);
+
 void igt_sysfs_engines(int xe, int engines, int gt, bool all, const char **property,
 		       void (*test)(int, int, const char **, uint16_t, int));
 
-- 
2.43.0