ChangeSet 1.1595.7.32, 2003/07/31 22:50:47-07:00, [EMAIL PROTECTED]
[PATCH] USB: usb_unlink_urb() kerneldoc
This been sitting in my queue for ages now ... it just
clarifies three points about unlink semantics. Basically,
- You can only unlink once per submission.
- For synchronous unlink: urb completes, then unlink returns.
- For async unlink: the order is unspecified; although usually
the completion happens after unlink returns.
drivers/usb/core/urb.c | 27 ++++++++++++++++-----------
1 files changed, 16 insertions(+), 11 deletions(-)
diff -Nru a/drivers/usb/core/urb.c b/drivers/usb/core/urb.c
--- a/drivers/usb/core/urb.c Fri Aug 1 10:53:55 2003
+++ b/drivers/usb/core/urb.c Fri Aug 1 10:53:55 2003
@@ -379,24 +379,29 @@
* usb_unlink_urb - abort/cancel a transfer request for an endpoint
* @urb: pointer to urb describing a previously submitted request
*
- * This routine cancels an in-progress request. The requests's
- * completion handler will be called with a status code indicating
- * that the request has been canceled, and that control of the URB
- * has been returned to that device driver.
+ * This routine cancels an in-progress request. URBs complete only
+ * once per submission, and may be canceled only once per submission.
+ * Successful cancelation means the requests's completion handler will
+ * be called with a status code indicating that the request has been
+ * canceled (rather than any other code) and will quickly be removed
+ * from host controller data structures.
*
* When the URB_ASYNC_UNLINK transfer flag for the URB is clear, this
* request is synchronous. Success is indicated by returning zero,
- * at which time the urb will have been unlinked,
- * and the completion function will see status -ENOENT. Failure is
- * indicated by any other return value. This mode may not be used
+ * at which time the urb will have been unlinked and its completion
+ * handler will have been called with urb->status -ENOENT. Failure is
+ * indicated by any other return value.
+ *
+ * The synchronous cancelation mode may not be used
* when unlinking an urb from an interrupt context, such as a bottom
- * half or a completion handler,
+ * half or a completion handler; or when holding a spinlock; or in
+ * other cases when the caller can't schedule().
*
* When the URB_ASYNC_UNLINK transfer flag for the URB is set, this
* request is asynchronous. Success is indicated by returning -EINPROGRESS,
- * at which time the urb will normally not have been unlinked,
- * and the completion function will see status -ECONNRESET. Failure is
- * indicated by any other return value.
+ * at which time the urb will normally not have been unlinked.
+ * The completion function will see urb->status -ECONNRESET. Failure
+ * is indicated by any other return value.
*/
int usb_unlink_urb(struct urb *urb)
{
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