EHCI: force high-speed devices to run at full speed

This patch (as710) adds a sysfs class-device attribute file named
"companion" for EHCI controllers.  The file contains a list of port
numbers that are dedicated to the companion controller; by writing a
port number to the file the user can force a high-speed device
attached directly to the computer to run at full speed.  (As far as I
know it is not possible to do this for a device attached to an
external hub.)  A port is removed from the file by writing the
negative of its port number.

Several users have asked for this facility and it seems like a useful
thing to have.  Every now and then one runs across a device which
behaves much better at full speed than at high speed.

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Cc: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

1 files changed, 2 insertions, 0 deletions

diff --git a/drivers/usb/host/ehci-hcd.c b/drivers/usb/host/ehci-hcd.c
index 9ec896218feb..92c62911f574 100644
--- a/drivers/usb/host/ehci-hcd.c
+++ b/drivers/usb/host/ehci-hcd.c
@@ -388,6 +388,7 @@ static void ehci_stop (struct usb_hcd *hcd)
 	/* let companion controllers work when we aren't */
 	ehci_writel(ehci, 0, &ehci->regs->configured_flag);
 
+	remove_companion_file(ehci);
 	remove_debug_files (ehci);
 
 	/* root hub is shut down separately (first, when possible) */
@@ -563,6 +564,7 @@ static int ehci_run (struct usb_hcd *hcd)
 	 * since the class device isn't created that early.
 	 */
 	create_debug_files(ehci);
+	create_companion_file(ehci);
 
 	return 0;
 }