USB Gadget: documentation update
This patch (as1102) clarifies two points in the USB Gadget kerneldoc:
Request completion callbacks are always made with interrupts
disabled;
Device controllers may not support STALLing the status stage
of a control transfer after the data stage is over.
Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Acked-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
diff --git a/include/linux/usb/gadget.h b/include/linux/usb/gadget.h
index 0ebedae..0460a74 100644
--- a/include/linux/usb/gadget.h
+++ b/include/linux/usb/gadget.h
@@ -33,7 +33,8 @@
* @short_not_ok: When reading data, makes short packets be
* treated as errors (queue stops advancing till cleanup).
* @complete: Function called when request completes, so this request and
- * its buffer may be re-used.
+ * its buffer may be re-used. The function will always be called with
+ * interrupts disabled, and it must not sleep.
* Reads terminate with a short packet, or when the buffer fills,
* whichever comes first. When writes terminate, some data bytes
* will usually still be in flight (often in a hardware fifo).
@@ -271,7 +272,10 @@
* (Note that some USB device controllers disallow protocol stall responses
* in some cases.) When control responses are deferred (the response is
* written after the setup callback returns), then usb_ep_set_halt() may be
- * used on ep0 to trigger protocol stalls.
+ * used on ep0 to trigger protocol stalls. Depending on the controller,
+ * it may not be possible to trigger a status-stage protocol stall when the
+ * data stage is over, that is, from within the response's completion
+ * routine.
*
* For periodic endpoints, like interrupt or isochronous ones, the usb host
* arranges to poll once per interval, and the gadget driver usually will