Re: USB Storage Device Not Working

On Wed, Nov 07, 2007 at 05:19:00PM -0500, Alan Stern wrote:
> On Thu, 8 Nov 2007, balajirrao wrote:
> 
> > > Right now the kernel doesn't have any means for automatically forcing
> > > devices to run at full speed when they fail to enumerate at high speed,
> > > although adding such a feature might not be a bad idea.  However you
> > > can force a particular USB port to run at full speed by hand.  The
> > > command is:
> > > 
> > > 	echo P >/sys/class/usb_host/usb_hostN/companion
> > > 
> > > where P is the port number and N is the bus number of the EHCI 
> > > controller.
> > > 
> > Thank you very much for the command. It worked fine.
> > And, about that feature - I am interested in developing it. Can you
> > please help me as to how to go about it ? 
> 
> You will have to add a new method pointer to struct usb_hcd, maybe call
> it "relinquish".  In ehci-hub.c make the method routine check that its
> argument really is attached to a port on the root hub and hand that
> port over to the companion controller.  Then in hub.c if
> hub_port_connect_change() fails, make it invoke this new method.
> 
I have done what you have told with a few additional changes. This is my
first real patch. So, please tell me where i am wrong. I just made it
work. Dont know whether its the right way to do it. Please tell.

Also, there is one more problem. When the device which is forced to work
by the kernel to work under companion is removed, the port should be
removed from the companion list. Otherwise, when another high speed
device is plugged into the same port, it would work in full speed.

So, my idea is to have a variable called forced_companion_ports, and a
method called un_relinqush, which takes care of removing the forced from
the companion list. But i didnt know from where to call this function.
I tried calling it in the hub_port_connect_change function, but i got a
OOPS in which khubd was killed. So if i could know which port the
disconnected device was connected to, it would be helpful i guess.

The patch is inlined below. Please comment. (Please tell where i am
wrong. )

Index: linux-2.6.24-rc2-usb/drivers/usb/host/ehci-hcd.c
===================================================================
--- linux-2.6.24-rc2-usb.orig/drivers/usb/host/ehci-hcd.c
+++ linux-2.6.24-rc2-usb/drivers/usb/host/ehci-hcd.c
@@ -433,6 +433,13 @@ static void ehci_stop (struct usb_hcd *h
 		    ehci_readl(ehci, &ehci->regs->status));
 }
 
+static void relinquish_port (struct usb_hcd *hcd, int port_num) {
+	struct ehci_hcd *ehci;
+
+	ehci = hcd_to_ehci(hcd);
+ 	store_companion(ehci, port_num, PORT_OWNER);	
+}
+
 /* one-time init, only for memory state */
 static int ehci_init(struct usb_hcd *hcd)
 {
@@ -443,6 +450,8 @@ static int ehci_init(struct usb_hcd *hcd
 
 	spin_lock_init(&ehci->lock);
 
+	hcd->relinquish_port = relinquish_port;
+
 	init_timer(&ehci->watchdog);
 	ehci->watchdog.function = ehci_watchdog;
 	ehci->watchdog.data = (unsigned long) ehci;
Index: linux-2.6.24-rc2-usb/drivers/usb/host/ehci-hub.c
===================================================================
--- linux-2.6.24-rc2-usb.orig/drivers/usb/host/ehci-hub.c
+++ linux-2.6.24-rc2-usb/drivers/usb/host/ehci-hub.c
@@ -316,24 +316,12 @@ static ssize_t show_companion(struct cla
  * Syntax is "[-]portnum", where a leading '-' sign means
  * return control of the port to the EHCI controller.
  */
-static ssize_t store_companion(struct class_device *class_dev,
-		const char *buf, size_t count)
-{
-	struct ehci_hcd		*ehci;
-	int			portnum, new_owner, try;
+void store_companion(struct ehci_hcd *ehci, int portnum, int new_owner)
+{			
 	u32 __iomem		*status_reg;
 	u32			port_status;
-
-	ehci = hcd_to_ehci(bus_to_hcd(class_get_devdata(class_dev)));
-	new_owner = PORT_OWNER;		/* Owned by companion */
-	if (sscanf(buf, "%d", &portnum) != 1)
-		return -EINVAL;
-	if (portnum < 0) {
-		portnum = - portnum;
-		new_owner = 0;		/* Owned by EHCI */
-	}
-	if (portnum <= 0 || portnum > HCS_N_PORTS(ehci->hcs_params))
-		return -ENOENT;
+	int			try;
+	
 	status_reg = &ehci->regs->port_status[--portnum];
 	if (new_owner)
 		set_bit(portnum, &ehci->companion_ports);
@@ -341,10 +329,10 @@ static ssize_t store_companion(struct cl
 		clear_bit(portnum, &ehci->companion_ports);
 
 	/*
-	 * The controller won't set the OWNER bit if the port is
-	 * enabled, so this loop will sometimes require at least two
-	 * iterations: one to disable the port and one to set OWNER.
-	 */
+	* The controller won't set the OWNER bit if the port is
+	* enabled, so this loop will sometimes require at least two
+	* iterations: one to disable the port and one to set OWNER.
+	*/
 
 	for (try = 4; try > 0; --try) {
 		spin_lock_irq(&ehci->lock);
@@ -361,10 +349,29 @@ static ssize_t store_companion(struct cl
 		spin_unlock_irq(&ehci->lock);
 		if (try > 1)
 			msleep(5);
+	}	
+}
+
+static ssize_t sysfs_store_companion(struct class_device *class_dev,
+		const char *buf, size_t count) {
+	
+	struct ehci_hcd		*ehci;
+	int			portnum, new_owner;
+		
+	ehci = hcd_to_ehci(bus_to_hcd(class_get_devdata(class_dev)));
+	new_owner = PORT_OWNER;		/* Owned by companion */
+	if (sscanf(buf, "%d", &portnum) != 1)
+		return -EINVAL;
+	if (portnum < 0) {
+		portnum = - portnum;
+		new_owner = 0;		/* Owned by EHCI */
 	}
+	if (portnum <= 0 || portnum > HCS_N_PORTS(ehci->hcs_params))
+		return -ENOENT;
+	store_companion(ehci, portnum, new_owner);
 	return count;
 }
-static CLASS_DEVICE_ATTR(companion, 0644, show_companion, store_companion);
+static CLASS_DEVICE_ATTR(companion, 0644, show_companion, sysfs_store_companion);
 
 static inline void create_companion_file(struct ehci_hcd *ehci)
 {
Index: linux-2.6.24-rc2-usb/drivers/usb/core/hcd.h
===================================================================
--- linux-2.6.24-rc2-usb.orig/drivers/usb/core/hcd.h
+++ linux-2.6.24-rc2-usb/drivers/usb/core/hcd.h
@@ -90,6 +90,8 @@ struct usb_hcd {
 #define HCD_FLAG_HW_ACCESSIBLE	0x00000001
 #define HCD_FLAG_SAW_IRQ	0x00000002
 
+	void 		(*relinquish_port)(struct usb_hcd *, int port_num);
+
 	unsigned		rh_registered:1;/* is root hub registered? */
 
 	/* The next flag is a stopgap, to be removed when all the HCDs
@@ -110,6 +112,7 @@ struct usb_hcd {
 	struct dma_pool		*pool [HCD_BUFFER_POOLS];
 
 	int			state;
+	
 #	define	__ACTIVE		0x01
 #	define	__SUSPEND		0x04
 #	define	__TRANSIENT		0x80
Index: linux-2.6.24-rc2-usb/drivers/usb/core/hub.c
===================================================================
--- linux-2.6.24-rc2-usb.orig/drivers/usb/core/hub.c
+++ linux-2.6.24-rc2-usb/drivers/usb/core/hub.c
@@ -2484,6 +2484,7 @@ static void hub_port_connect_change(stru
 	struct device *hub_dev = hub->intfdev;
 	u16 wHubCharacteristics = le16_to_cpu(hub->descriptor->wHubCharacteristics);
 	int status, i;
+	struct usb_hcd *hcd;
  
 	dev_dbg (hub_dev,
 		"port %d, status %04x, change %04x, %s\n",
@@ -2644,6 +2645,9 @@ loop:
 	}
  
 done:
+	hcd = bus_to_hcd(hub->hdev->bus);
+	if (hcd->relinquish_port)
+		hcd->relinquish_port(hcd, port1);
 	hub_port_disable(hub, port1, 1);
 }

--

regards,
balaji rao 

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