Re: requirements for suspend()

Am Freitag, 4. Mai 2007 06:47 schrieb Greg KH:
> On Thu, May 03, 2007 at 11:05:54AM -0400, Alan Stern wrote:
> > On Thu, 3 May 2007, Oliver Neukum wrote:
> > 
> > > Am Donnerstag, 3. Mai 2007 16:03 schrieb Alan Stern:
> > > > On Thu, 3 May 2007, Oliver Neukum wrote:
> > > > 
> > > > > > > How about exporting usb_disable_interface() and usb_enable_interface()?
> > > > > > > It doesn't solve the problem for endpoint 0, but this case is rare.
> > > > > > 
> > > > > > We could; it would save drivers the trouble of keeping track of their own 
> > > > > > URBs.  Do you have a particular driver in mind for this?
> > > > > 
> > > > > Everything derived from newer versions of the skeleton driver.
> > > > 
> > > > Would we be better off modifying the skeleton driver to keep track of its 
> > > > own URBs?
> > > 
> > > I am unsure. The "fire-and-forget" technique is certainly simple for
> > > driver writers. Perhaps we should make it easier to keep track of URBs.
> > > A list_head in the URB?
> > 
> > People have discussed adding one in the past.  Greg might have some 
> > opinions.
> 
> My opinion is that we need to ensure that we can still do the
> "fire-and-forget" type driver :)

And this can be done. What do you think:

--- a/include/linux/usb.h	2007-05-04 10:50:18.000000000 +0200
+++ b/include/linux/usb.h	2007-05-04 14:10:49.000000000 +0200
@@ -958,11 +958,23 @@ struct usb_iso_packet_descriptor {
 
 struct urb;
 
+struct usb_anchor {
+	struct list_head urb_list;
+	spinlock_t lock;
+};
+
+static inline void init_usb_anchor(struct usb_anchor *anchor)
+{
+	INIT_LIST_HEAD(&anchor->urb_list);
+	spin_lock_init(&anchor->lock);
+}
+
 typedef void (*usb_complete_t)(struct urb *);
 
 /**
  * struct urb - USB Request Block
  * @urb_list: For use by current owner of the URB.
+ * @anchor: to anchor URBs to a common mooring
  * @pipe: Holds endpoint number, direction, type, and more.
  *	Create these values with the eight macros available;
  *	usb_{snd,rcv}TYPEpipe(dev,endpoint), where the TYPE is "ctrl"
@@ -1135,6 +1147,8 @@ struct urb
 	/* public: documented fields in the urb that can be used by drivers */
 	struct list_head urb_list;	/* list head for use by the urb's
 					 * current owner */
+	struct list_head anchor_list;	/* the URB may be anchored by the driver */
+	struct usb_anchor *anchor;
 	struct usb_device *dev; 	/* (in) pointer to associated device */
 	unsigned int pipe;		/* (in) pipe information */
 	int status;			/* (return) non-ISO status */
@@ -1270,6 +1284,8 @@ extern struct urb *usb_get_urb(struct ur
 extern int usb_submit_urb(struct urb *urb, gfp_t mem_flags);
 extern int usb_unlink_urb(struct urb *urb);
 extern void usb_kill_urb(struct urb *urb);
+extern void usb_associate_urb_to_anchor(struct urb *u, struct usb_anchor *a);
+extern void usb_kill_associated_urbs(struct usb_anchor *old, struct usb_anchor *new);
 
 void *usb_buffer_alloc (struct usb_device *dev, size_t size,
 	gfp_t mem_flags, dma_addr_t *dma);
--- a/drivers/usb/core/hcd.c	2007-05-04 12:04:29.000000000 +0200
+++ b/drivers/usb/core/hcd.c	2007-05-04 12:16:28.000000000 +0200
@@ -1408,6 +1408,15 @@ void usb_hcd_giveback_urb (struct usb_hc
 	}
 
 	usbmon_urb_complete (&hcd->self, urb);
+	if (urb->anchor) {
+		struct usb_anchor *anchor = urb->anchor;
+
+		spin_lock(&anchor->lock);
+		list_del(&urb->anchor_list);
+		urb->anchor = NULL;
+		spin_unlock(&anchor->lock);
+	}
+
 	/* pass ownership to the completion handler */
 	urb->complete (urb);
 	atomic_dec (&urb->use_count);
--- a/drivers/usb/core/urb.c	2007-05-04 10:53:14.000000000 +0200
+++ b/drivers/usb/core/urb.c	2007-05-04 14:28:29.000000000 +0200
@@ -11,6 +11,14 @@
 static void urb_destroy(struct kref *kref)
 {
 	struct urb *urb = to_urb(kref);
+	unsigned long flags;
+
+	if (urb->anchor) {
+		spin_lock_irqsave(&urb->anchor->lock, flags);
+		list_del(&urb->anchor_list);
+		spin_unlock_irqrestore(&urb->anchor->lock, flags);
+	}
+	
 	kfree(urb);
 }
 
@@ -34,6 +42,7 @@ void usb_init_urb(struct urb *urb)
 		memset(urb, 0, sizeof(*urb));
 		kref_init(&urb->kref);
 		spin_lock_init(&urb->lock);
+		INIT_LIST_HEAD(&urb->anchor_list);
 	}
 }
 
@@ -100,6 +109,25 @@ struct urb * usb_get_urb(struct urb *urb
 		kref_get(&urb->kref);
 	return urb;
 }
+
+/**
+ * usb_associate_urb_to_anchor - anchors an URB while it is processed
+ * @u: pointer to the urb to anchor
+ * @a: pointer to the anchor
+ *
+ * This can be called to have access to URBs which are to be executed
+ * without bothering to track them
+ */
+
+void usb_associate_urb_to_anchor(struct urb *u, struct usb_anchor *a)
+{
+	unsigned long flags;
+
+	spin_lock_irqsave(&a->lock, flags);
+	list_add_tail(&u->anchor_list, &a->urb_list);
+	u->anchor = a;
+	spin_unlock_irqrestore(&a->lock, flags);
+}
 		
 		
 /*-------------------------------------------------------------------*/
@@ -477,12 +505,45 @@ void usb_kill_urb(struct urb *urb)
 	--urb->reject;
 	spin_unlock_irq(&urb->lock);
 }
+/**
+ * usb_kill_associated_urbs - cancel transfer requests en masse
+ * @old: anchor the requests are bound to
+ * @new: anchor the request which were canceled shall be bound to, may be NULL
+ *
+ * this allows all outstanding URBs to be cancelled and bound to an anchor
+ * for later processing
+ */
+
+void usb_kill_associated_urbs(struct usb_anchor *old, struct usb_anchor *new)
+{
+	unsigned long flags;
+	struct urb *victim;
+
+	spin_lock_irqsave(&old->lock, flags);
+	while (!list_empty(&old->urb_list)) {
+		victim = list_entry(old->urb_list.prev, struct urb, anchor_list);
+		list_del(&victim->anchor_list);
+		/* we must make sure the URB isn't freed before we kill it*/
+		usb_get_urb(victim);
+		spin_unlock_irqrestore(&old->lock, flags);
+		usb_kill_urb(victim);
+		/* we may transfer only if we killed */
+		if (new && victim->status == -ENOENT)
+			list_add(&victim->anchor_list, &new->urb_list);
+		else
+			usb_put_urb(victim);
+		spin_lock_irqsave(&old->lock, flags);
+	}
+	spin_unlock_irqrestore(&old->lock, flags);
+}
 
 EXPORT_SYMBOL(usb_init_urb);
 EXPORT_SYMBOL(usb_alloc_urb);
 EXPORT_SYMBOL(usb_free_urb);
 EXPORT_SYMBOL(usb_get_urb);
+EXPORT_SYMBOL(usb_associate_urb_to_anchor);
 EXPORT_SYMBOL(usb_submit_urb);
 EXPORT_SYMBOL(usb_unlink_urb);
 EXPORT_SYMBOL(usb_kill_urb);
+EXPORT_SYMBOL(usb_kill_associated_urbs);
 
--- a/drivers/usb/usb-skeleton.c	2007-05-04 13:07:30.000000000 +0200
+++ b/drivers/usb/usb-skeleton.c	2007-05-04 14:11:50.000000000 +0200
@@ -54,10 +54,13 @@ struct usb_skel {
 	struct usb_device	*udev;			/* the usb device for this device */
 	struct usb_interface	*interface;		/* the interface for this device */
 	struct semaphore	limit_sem;		/* limiting the number of writes in progress */
+	struct usb_anchor	submitted;		/* in case we need to retract our submissions */
+	struct usb_anchor	redo;			/* to be redone in case of suspend or reset */
 	unsigned char           *bulk_in_buffer;	/* the buffer to receive data */
 	size_t			bulk_in_size;		/* the size of the receive buffer */
 	__u8			bulk_in_endpointAddr;	/* the address of the bulk in endpoint */
 	__u8			bulk_out_endpointAddr;	/* the address of the bulk out endpoint */
+	unsigned char		revoking;		/* this is set while submissions are revoked */
 	struct kref		kref;
 	struct mutex		io_mutex;		/* synchronize I/O with disconnect */
 };
@@ -185,11 +188,17 @@ static void skel_write_bulk_callback(str
 	      urb->status == -ESHUTDOWN)) {
 		err("%s - nonzero write bulk status received: %d",
 		    __FUNCTION__, urb->status);
+		/* the device is to be suspend,
+		   this urb must be redone,
+		   the buffer cannot be freed */
+		if (urb->status == -ENOENT && dev->revoking)
+			goto spare_buffer;
 	}
 
 	/* free up our allocated buffer */
 	usb_buffer_free(urb->dev, urb->transfer_buffer_length,
 			urb->transfer_buffer, urb->transfer_dma);
+spare_buffer:
 	up(&dev->limit_sem);
 }
 
@@ -244,6 +253,7 @@ static ssize_t skel_write(struct file *f
 			  usb_sndbulkpipe(dev->udev, dev->bulk_out_endpointAddr),
 			  buf, writesize, skel_write_bulk_callback, dev);
 	urb->transfer_flags |= URB_NO_TRANSFER_DMA_MAP;
+	usb_associate_urb_to_anchor(urb, &dev->submitted);
 
 	/* send the data out the bulk port */
 	retval = usb_submit_urb(urb, GFP_KERNEL);
@@ -306,6 +316,8 @@ static int skel_probe(struct usb_interfa
 	kref_init(&dev->kref);
 	sema_init(&dev->limit_sem, WRITES_IN_FLIGHT);
 	mutex_init(&dev->io_mutex);
+	init_usb_anchor(&dev->submitted);
+	init_usb_anchor(&dev->redo);
 
 	dev->udev = usb_get_dev(interface_to_usbdev(interface));
 	dev->interface = interface;
@@ -391,10 +403,57 @@ static void skel_disconnect(struct usb_i
 	info("USB Skeleton #%d now disconnected", minor);
 }
 
+static int skel_suspend(struct usb_interface *intf, pm_message_t message)
+{
+	struct usb_skel *dev= usb_get_intfdata(intf);
+
+	mutex_lock(&dev->io_mutex);
+	dev->revoking = 1;
+	usb_kill_associated_urbs(&dev->submitted, &dev->redo);
+	mutex_unlock(&dev->io_mutex);
+
+	return 0;
+}
+
+static int skel_resume (struct usb_interface *intf)
+{
+	struct usb_skel *dev= usb_get_intfdata(intf);
+	struct urb *lazarus, *n;
+	int r;
+
+	mutex_lock(&dev->io_mutex);
+	dev->revoking = 0;
+	list_for_each_entry_safe(lazarus, n, &dev->redo.urb_list, anchor_list) {
+		list_del(&lazarus->anchor_list);
+		usb_associate_urb_to_anchor(lazarus, &dev->submitted);
+		r = usb_submit_urb(lazarus, GFP_NOIO);
+		if (r < 0) {
+			/* if URB submission fails, it, its buffer and those
+			   after it and their buffers must be freed */
+			err("Could not redo URBs during resume");
+			usb_buffer_free(lazarus->dev, lazarus->transfer_buffer_length,
+			lazarus->transfer_buffer, lazarus->transfer_dma);
+			usb_free_urb(lazarus);
+			list_for_each_entry_safe(lazarus, n, &dev->redo.urb_list, anchor_list) {
+				usb_buffer_free(lazarus->dev, lazarus->transfer_buffer_length,
+				lazarus->transfer_buffer, lazarus->transfer_dma);
+				usb_free_urb(lazarus);	
+			}
+			mutex_unlock(&dev->io_mutex);
+			return r;
+		}
+		usb_free_urb(lazarus);
+	}
+	mutex_unlock(&dev->io_mutex);
+	return 0;
+}
+
 static struct usb_driver skel_driver = {
 	.name =		"skeleton",
 	.probe =	skel_probe,
 	.disconnect =	skel_disconnect,
+	.suspend =	skel_suspend,
+	.resume =	skel_resume,
 	.id_table =	skel_table,
 	.supports_autosuspend = 1,
 };

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