[PATCH v5 1/3] lib/igt_sysfs: Add igt_sysfs_get_next_engine

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

Create a new helper function, igt_sysfs_get_next_engine, that iterates
over sysfs/engines and stores the next engine for the user.  The
function returns true if the next engine in the list is available, and
false otherwise.  The function will be used in the test suite in a later
patch.

Signed-off-by: Jonathan Cavitt <jonathan.cavitt@intel.com>
---
 lib/igt_sysfs.c | 36 ++++++++++++++++++++++++++++++++++++
 lib/igt_sysfs.h |  1 +
 2 files changed, 37 insertions(+)

diff --git a/lib/igt_sysfs.c b/lib/igt_sysfs.c
index 26a3aa31fb..3d0dada969 100644
--- a/lib/igt_sysfs.c
+++ b/lib/igt_sysfs.c
@@ -1236,6 +1236,42 @@ static uint16_t xe_get_engine_class(char *name)
 	return class;
 }
 
+/**
+ * igt_sysfs_get_next_engine:
+ * @engines: fd of the directory engine
+ * @prior: previous engine from the sysfs/engines list
+ *
+ * Iterates over sysfs/engines and stores the next engine in prior.
+ * Returns true if there are more engines to iterate over, and false otherwise.
+ */
+bool igt_sysfs_get_next_engine(int engines, int *prior)
+{
+	struct dirent *de;
+	DIR *dir;
+
+	if (!prior)
+		lseek(engines, 0, SEEK_SET);
+	else
+		close(*prior);
+
+	dir = fdopendir(engines);
+	if (!dir) {
+		close(engines);
+		return false;
+	}
+
+	while ((de = readdir(dir))) {
+		if (*de->d_name == '.')
+			continue;
+
+		*prior = openat(engines, de->d_name, O_RDONLY);
+		if (*prior >= 0)
+			return true;
+	}
+	return false;
+}
+
+
 /**
  * igt_sysfs_engines:
  * @xe: fd of the device
diff --git a/lib/igt_sysfs.h b/lib/igt_sysfs.h
index 852b95053f..bff5ed68e6 100644
--- a/lib/igt_sysfs.h
+++ b/lib/igt_sysfs.h
@@ -163,6 +163,7 @@ typedef struct igt_sysfs_rw_attr {
 
 void igt_sysfs_rw_attr_verify(igt_sysfs_rw_attr_t *rw);
 
+bool igt_sysfs_get_next_engine(int engines, int *prior);
 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