USB: remove LPM management from usb_driver_claim_interface()
authorAlan Stern <stern@rowland.harvard.edu>
Mon, 10 Sep 2018 17:58:51 +0000 (13:58 -0400)
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Thu, 20 Sep 2018 10:49:12 +0000 (12:49 +0200)
commitc183813fcee44a249339b7c46e1ad271ca1870aa
tree9cac1739e885c473b32c28cb1ce536912600cab6
parent81e0403b26d94360abd1f6a57311337973bc82cd
USB: remove LPM management from usb_driver_claim_interface()

usb_driver_claim_interface() disables and re-enables Link Power
Management, but it shouldn't do either one, for the reasons listed
below.  This patch removes the two LPM-related function calls from the
routine.

The reason for disabling LPM in the analogous function
usb_probe_interface() is so that drivers won't have to deal with
unwanted LPM transitions in their probe routine.  But
usb_driver_claim_interface() doesn't call the driver's probe routine
(or any other callbacks), so that reason doesn't apply here.

Furthermore, no driver other than usbfs will ever call
usb_driver_claim_interface() unless it is already bound to another
interface in the same device, which means disabling LPM here would be
redundant.  usbfs doesn't interact with LPM at all.

Lastly, the error return from usb_unlocked_disable_lpm() isn't handled
properly; the code doesn't clean up its earlier actions before
returning.

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Fixes: 8306095fd2c1 ("USB: Disable USB 3.0 LPM in critical sections.")
CC: <stable@vger.kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
drivers/usb/core/driver.c