[igt-dev] [PATCH i-g-t] i915/hangman: Read a dummy byte to check sysfs existence

[Chris Wilson <chris@chris-wilson.co.uk>]

sysfs doesn't give the driver an open() callback, so we can only report
the unavailability of HW on the first read; so check read() after checking
open().

Fixes: 93f0ad4b835e ("i915/hangman: Skip if disabled by the kernel")
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
---
 tests/i915/hangman.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/tests/i915/hangman.c b/tests/i915/hangman.c
index ffbd0b057..5f63bfc4b 100644
--- a/tests/i915/hangman.c
+++ b/tests/i915/hangman.c
@@ -45,14 +45,20 @@ static int sysfs = -1;
 
 static bool has_error_state(int dir)
 {
+	bool result;
 	int fd;
 
 	fd = openat(dir, "error", O_RDONLY);
 	if (fd < 0)
 		return false;
 
+	if (read(fd, &result, sizeof(result)) < 0)
+		result = false;
+	else
+		result = true;
+
 	close(fd);
-	return true;
+	return result;
 }
 
 static void assert_entry(const char *s, bool expect)
-- 
2.20.1

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