This patch (as1459) updates the documentation for the pre_reset method
in struct usb_driver. When a driver is notified of an impending
reset, it must cancel all outstanding I/O and not start any new I/O
until it has been notified that the reset is complete.
As far as I know, most existing drivers that implement pre_reset do
this now. The major exceptions appear to be the SpeedTouch and
CDC-WDM drivers.
Signed-off-by: Alan Stern <stern@xxxxxxxxxxxxxxxxxxx>
---
Documentation/usb/callbacks.txt | 8 +++++---
include/linux/usb.h | 6 ++++--
2 files changed, 9 insertions(+), 5 deletions(-)
Index: usb-2.6/include/linux/usb.h
===================================================================
--- usb-2.6.orig/include/linux/usb.h
+++ usb-2.6/include/linux/usb.h
@@ -806,8 +806,10 @@ struct usbdrv_wrap {
* @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.
- * @pre_reset: Called by usb_reset_device() when the device
- * is about to be reset.
+ * @pre_reset: Called by usb_reset_device() when the device is about to be
+ * reset. This routine must not return until the driver has no active
+ * URBs for the device, and no more URBs may be submitted until the
+ * post_reset method is called.
* @post_reset: Called by usb_reset_device() after the device
* has been reset
* @id_table: USB drivers use ID table to support hotplugging.
Index: usb-2.6/Documentation/usb/callbacks.txt
===================================================================
--- usb-2.6.orig/Documentation/usb/callbacks.txt
+++ usb-2.6/Documentation/usb/callbacks.txt
@@ -95,9 +95,11 @@ pre_reset
int (*pre_reset)(struct usb_interface *intf);
-Another driver or user space is triggering a reset on the device which
-contains the interface passed as an argument. Cease IO and save any
-device state you need to restore.
+A driver or user space is triggering a reset on the device which
+contains the interface passed as an argument. Cease IO, wait for all
+outstanding URBs to complete, and save any device state you need to
+restore. No more URBs may be submitted until the post_reset method
+is called.
If you need to allocate memory here, use GFP_NOIO or GFP_ATOMIC, if you
are in atomic context.
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