drm/xe/debugfs: fixed the return value of wedged_mode_set

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@intel.com>
Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Cc: Fei Yang <fei.yang@intel.com>
Cc: Shuicheng Lin <shuicheng.lin@intel.com>
Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20250213223615.2327367-1-x.wang@intel.com
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>

diff --git a/drivers/gpu/drm/xe/xe_debugfs.c b/drivers/gpu/drm/xe/xe_debugfs.c
index 761e00cb64371c42e12e5ba4f6d861f41c2fb5b3..d0503959a8ed09c3f5d5f514ca75e2d4d5c639e7 100644 (file)
--- 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;