[PATCH] drm/xe/debugfs: fixed the return value of wedged_mode_set

[Xin Wang]

It is generally expected that the write() function should return a
positive value indicating the number of bytes written or a negative
error code if an error occurs. Returning 0 is unusual and can lead
to unexpected behavior.

When the user program writes the same value to wedged_mode twice in
a row, a lockup will occur, because the value expected to be
returned by the write() function inside the program should be equal
to the actual written value instead of 0.

To reproduce the issue:
echo 1 > /sys/kernel/debug/dri/0/wedged_mode
echo 1 > /sys/kernel/debug/dri/0/wedged_mode   <- lockup here

Signed-off-by: Xin Wang <x.wang at intel.com>
Cc: Rodrigo Vivi <rodrigo.vivi at intel.com>
Cc: Fei Yang <fei.yang at intel.com>
Cc: Shuicheng Lin <shuicheng.lin at intel.com>
---
 drivers/gpu/drm/xe/xe_debugfs.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/xe/xe_debugfs.c b/drivers/gpu/drm/xe/xe_debugfs.c
index 56cb3788e752..b46075edf60a 100644
--- a/drivers/gpu/drm/xe/xe_debugfs.c
+++ b/drivers/gpu/drm/xe/xe_debugfs.c
@@ -167,7 +167,7 @@ static ssize_t wedged_mode_set(struct file *f, const char __user *ubuf,
 		return -EINVAL;
 
 	if (xe->wedged.mode == wedged_mode)
-		return 0;
+		return size;
 
 	xe->wedged.mode = wedged_mode;
 
-- 
2.43.0