linux-kernel - Re: 2.6.25-rc6: CONFIG_USB

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Message-Id: <200806101055.14539.oliver@neukum.org>
Date:	Tue, 10 Jun 2008 10:55:13 +0200
From:	Oliver Neukum <oliver@...kum.org>
To:	Pavel Machek <pavel@...e.cz>, linux-usb@...r.kernel.org
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Greg KH <gregkh@...e.de>,
	Alan Stern <stern@...land.harvard.edu>,
	Linus Torvalds <torvalds@...uxfoundation.org>,
	Andrew Morton <akpm@...uxfoundation.org>,
	kernel list <linux-kernel@...r.kernel.org>,
	"Rafael J. Wysocki" <rjw@...k.pl>
Subject: Re: 2.6.25-rc6: CONFIG_USB_PERSIST forced on

Am Montag 09 Juni 2008 23:56:51 schrieb Pavel Machek:
> On Mon 2008-06-09 14:39:10, Linus Torvalds wrote:
> > 
> > 
> > On Mon, 9 Jun 2008, Pavel Machek wrote:
> > > 
> > > I believe we should just revert the "CONFIG_USB_PERSIST force on"
> > > patch, and solve this properly in 2.6.27.
> > 
> > Why?
> > 
> > The code would _still_ be buggy with that revert in place. You have to 
> > enable CONFIG_USB_PERSIST just to get even the _possibility_ of the sane 
> > behavior. 
> > 
> > If there is a problem with usblp, it just needs to be fixed. 
> 
> With USB_PERSIST on, you have problem on all drivers but usb-storage,
> AFAICT... because usb-storage seems to be the only driver implementing
> reset_resume.
> 
> I guess it is possible to do something like "if reset_resume() is
> unavailable, try plain resume()" in usb/driver.c, but I'd really
> changes to the suspend/resume callback to go in -rc1 so that they are
> tested properly, and not hot-patch it now.

If a hotfix it must be, here's my take. It works for me, but it isn't
tested well.
Alan, what do you think?

	Regards
		Oliver

Signed-off-by: Oliver Neukum <oneukum@...e.de>

---

--- linux-2.6.25/drivers/usb/core/hub.c	2008-06-09 15:15:13.105058000 +0200
+++ alt/drivers/usb/core/hub.c	2008-06-09 15:43:29.964503000 +0200
@@ -648,7 +648,9 @@ static void hub_stop(struct usb_hub *hub
 static void hub_restart(struct usb_hub *hub, int type)
 {
 	struct usb_device *hdev = hub->hdev;
-	int port1;
+	struct usb_interface *intf;
+	struct usb_driver *driver;
+	int port1, i;
 
 	/* Check each of the children to see if they require
 	 * USB-PERSIST handling or disconnection.  Also check
@@ -692,6 +694,14 @@ static void hub_restart(struct usb_hub *
 		 */
 		if (udev->persist_enabled && status == 0 &&
 				!(portstatus & USB_PORT_STAT_ENABLE)) {
+
+			/* check for devices not supporting reset_resume */
+			for (i = 0; i < udev->actconfig->desc.bNumInterfaces; i++) {
+				intf = udev->actconfig->interface[i];
+				driver = to_usb_driver(intf->dev.driver);
+				if (!driver || !driver->reset_resume)
+					goto skip_reset_resume;
+			}
 			if (portchange & USB_PORT_STAT_C_ENABLE)
 				clear_port_feature(hub->hdev, port1,
 						USB_PORT_FEAT_C_ENABLE);
@@ -705,8 +715,11 @@ static void hub_restart(struct usb_hub *
 		 * but as we may not lock the child device here
 		 * we have to do a "logical" disconnect.
 		 */
-		else if (type == HUB_RESET_RESUME)
-			hub_port_logical_disconnect(hub, port1);
+		else {
+skip_reset_resume:
+			if (type == HUB_RESET_RESUME)
+				hub_port_logical_disconnect(hub, port1);
+		}
 	}
 
 	hub_activate(hub);
--
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