USB: adds comment on suspend callback

This patch adds comments on interface driver suspend callback
to emphasize that the failure return value is ignored by
USB core in system sleep context, so do not try to recover
device for this case and let resume/reset_resume callback
handle the suspend failure if needed.

Also kerneldoc for usb_suspend_both() is updated with the
fact.

Acked-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Ming Lei <ming.lei@canonical.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 6 insertions, 1 deletions

diff --git a/include/linux/usb.h b/include/linux/usb.h
index 52464fb2389b..8d4bc173d66a 100644
--- a/include/linux/usb.h
+++ b/include/linux/usb.h
@@ -976,7 +976,12 @@ struct usbdrv_wrap {
  *	the "usbfs" filesystem.  This lets devices provide ways to
  *	expose information to user space regardless of where they
  *	do (or don't) show up otherwise in the filesystem.
- * @suspend: Called when the device is going to be suspended by the system.
+ * @suspend: Called when the device is going to be suspended by the
+ *	system either from system sleep or runtime suspend context. The
+ *	return value will be ignored in system sleep context, so do NOT
+ *	try to continue using the device if suspend fails in this case.
+ *	Instead, let the resume or reset-resume routine recover from
+ *	the failure.
  * @resume: Called when the device is being resumed by the system.
  * @reset_resume: Called when the suspended device has been reset instead
  *	of being resumed.