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| author | Alan Stern <stern@rowland.harvard.edu> | 2014-03-18 18:39:05 +0400 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2014-03-20 01:00:32 +0400 |
| commit | 1d10255c1c496557a5674e651c4ebbe0f61279f2 (patch) | |
| tree | 7d65e464bc4ba39240f124111c8c4d30dd7e76e8 | |
| parent | 6aec044cc2f5670cf3b143c151c8be846499bd15 (diff) | |
| download | linux-1d10255c1c496557a5674e651c4ebbe0f61279f2.tar.xz | |
USB: disable reset-resume when USB_QUIRK_RESET is set
The USB_QUIRK_RESET flag indicates that a USB device changes its
identity in some way when it is reset. It may lose its firmware, its
descriptors may change, or it may switch back to a default mode of
operation.
If a device does this, the kernel needs to avoid resetting it. Resets
are likely to fail, or worse, succeed while changing the device's
state in a way the system can't detect.
This means we should disable the reset-resume mechanism whenever this
quirk flag is present. An attempted reset-resume will fail, the
device will be logically disconnected, and later on the hub driver
will rediscover and re-enumerate the device. This will cause the
appropriate udev events to be generated, so that userspace will have a
chance to switch the device into its normal operating mode, if
necessary.
Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
CC: Oliver Neukum <oliver@neukum.org>
Reviewed-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
| -rw-r--r-- | drivers/usb/core/hub.c | 14 |
1 files changed, 12 insertions, 2 deletions
diff --git a/drivers/usb/core/hub.c b/drivers/usb/core/hub.c index 2d74dfb9c989..d670aaf13a3d 100644 --- a/drivers/usb/core/hub.c +++ b/drivers/usb/core/hub.c @@ -3105,9 +3105,19 @@ static int finish_port_resume(struct usb_device *udev) * operation is carried out here, after the port has been * resumed. */ - if (udev->reset_resume) + if (udev->reset_resume) { + /* + * If the device morphs or switches modes when it is reset, + * we don't want to perform a reset-resume. We'll fail the + * resume, which will cause a logical disconnect, and then + * the device will be rediscovered. + */ retry_reset_resume: - status = usb_reset_and_verify_device(udev); + if (udev->quirks & USB_QUIRK_RESET) + status = -ENODEV; + else + status = usb_reset_and_verify_device(udev); + } /* 10.5.4.5 says be sure devices in the tree are still there. * For now let's assume the device didn't go crazy on resume, |