[Intel-gfx] [PATCH i-g-t] i915/gem_exec_capture: Check the strlen() for an empty file

[Chris Wilson]

igt_sysfs_get() only returns NULL if the open() fails, and a valid
string otherwise. So if the read() fails with ENODEV (because sysfs
doesn't provide the driver with an ->open() callback), we return an
empty string, and "No error captured" otherwise.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=109481
Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
---
 tests/i915/gem_exec_capture.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/tests/i915/gem_exec_capture.c b/tests/i915/gem_exec_capture.c
index eca73ab11..56837dfca 100644
--- a/tests/i915/gem_exec_capture.c
+++ b/tests/i915/gem_exec_capture.c
@@ -519,6 +519,11 @@ static bool has_capture(int fd)
 	return async > 0;
 }
 
+static size_t safer_strlen(const char *s)
+{
+	return s ? strlen(s) : 0;
+}
+
 igt_main
 {
 	const struct intel_execution_engine *e;
@@ -544,7 +549,7 @@ igt_main
 
 		dir = igt_sysfs_open(fd, NULL);
 		igt_require(igt_sysfs_set(dir, "error", "Begone!"));
-		igt_require(igt_sysfs_get(dir, "error"));
+		igt_require(safer_strlen(igt_sysfs_get(dir, "error")) > 0);
 	}
 
 	for (e = intel_execution_engines; e->name; e++) {
-- 
2.20.1