USB: remove CONFIG_USB_PERSIST setting
This patch (as1047) removes the USB_PERSIST Kconfig option, enabling it permanently. It also prevents the power/persist attribute from being created for hub devices; there's no point in having it since USB-PERSIST is always turned on for hubs. Signed-off-by: Alan Stern <stern@rowland.harvard.edu> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
This commit is contained in:
Alan Stern
Greg Kroah-Hartman
parent
5e6effaed6
commit
feccc30d90
7 changed files with 53 additions and 81 deletions
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@ -2,7 +2,7 @@
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Alan Stern <stern@rowland.harvard.edu>
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September 2, 2006 (Updated May 29, 2007)
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September 2, 2006 (Updated February 25, 2008)
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What is the problem?
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@ -65,9 +65,10 @@ much better.)
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What is the solution?
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Setting CONFIG_USB_PERSIST will cause the kernel to work around these
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issues. It enables a mode in which the core USB device data
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structures are allowed to persist across a power-session disruption.
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The kernel includes a feature called USB-persist. It tries to work
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around these issues by allowing the core USB device data structures to
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persist across a power-session disruption.
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It works like this. If the kernel sees that a USB host controller is
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not in the expected state during resume (i.e., if the controller was
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reset or otherwise had lost power) then it applies a persistence check
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@ -80,28 +81,30 @@ re-enumeration shows that the device now attached to that port has the
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same descriptors as before, including the Vendor and Product IDs, then
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the kernel continues to use the same device structure. In effect, the
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kernel treats the device as though it had merely been reset instead of
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unplugged.
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unplugged. The same thing happens if the host controller is in the
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expected state but a USB device was unplugged and then replugged.
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If no device is now attached to the port, or if the descriptors are
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different from what the kernel remembers, then the treatment is what
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you would expect. The kernel destroys the old device structure and
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behaves as though the old device had been unplugged and a new device
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plugged in, just as it would without the CONFIG_USB_PERSIST option.
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plugged in.
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The end result is that the USB device remains available and usable.
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Filesystem mounts and memory mappings are unaffected, and the world is
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now a good and happy place.
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Note that even when CONFIG_USB_PERSIST is set, the "persist" feature
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will be applied only to those devices for which it is enabled. You
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can enable the feature by doing (as root):
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Note that the "USB-persist" feature will be applied only to those
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devices for which it is enabled. You can enable the feature by doing
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(as root):
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echo 1 >/sys/bus/usb/devices/.../power/persist
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where the "..." should be filled in the with the device's ID. Disable
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the feature by writing 0 instead of 1. For hubs the feature is
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automatically and permanently enabled, so you only have to worry about
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setting it for devices where it really matters.
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automatically and permanently enabled and the power/persist file
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doesn't even exist, so you only have to worry about setting it for
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devices where it really matters.
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Is this the best solution?
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@ -112,19 +115,19 @@ centralized Logical Volume Manager. Such a solution would allow you
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to plug in a USB flash device, create a persistent volume associated
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with it, unplug the flash device, plug it back in later, and still
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have the same persistent volume associated with the device. As such
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it would be more far-reaching than CONFIG_USB_PERSIST.
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it would be more far-reaching than USB-persist.
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On the other hand, writing a persistent volume manager would be a big
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job and using it would require significant input from the user. This
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solution is much quicker and easier -- and it exists now, a giant
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point in its favor!
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Furthermore, the USB_PERSIST option applies to _all_ USB devices, not
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Furthermore, the USB-persist feature applies to _all_ USB devices, not
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just mass-storage devices. It might turn out to be equally useful for
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other device types, such as network interfaces.
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WARNING: Using CONFIG_USB_PERSIST can be dangerous!!
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WARNING: USB-persist can be dangerous!!
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When recovering an interrupted power session the kernel does its best
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to make sure the USB device hasn't been changed; that is, the same
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@ -152,5 +155,5 @@ but yourself.
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YOU HAVE BEEN WARNED! USE AT YOUR OWN RISK!
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That having been said, most of the time there shouldn't be any trouble
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at all. The "persist" feature can be extremely useful. Make the most
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of it.
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at all. The USB-persist feature can be extremely useful. Make the
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most of it.
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@ -102,31 +102,6 @@ config USB_SUSPEND
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If you are unsure about this, say N here.
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config USB_PERSIST
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bool "USB device persistence during system suspend (DANGEROUS)"
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depends on USB && PM && EXPERIMENTAL
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default n
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help
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If you say Y here and enable the "power/persist" attribute
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for a USB device, the device's data structures will remain
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persistent across system suspend, even if the USB bus loses
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power. (This includes hibernation, also known as swsusp or
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suspend-to-disk.) The devices will reappear as if by magic
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when the system wakes up, with no need to unmount USB
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filesystems, rmmod host-controller drivers, or do anything
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else.
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WARNING: This option can be dangerous!
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If a USB device is replaced by another of the same type while
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the system is asleep, there's a good chance the kernel won't
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detect the change. Likewise if the media in a USB storage
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device is replaced. When this happens it's almost certain to
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cause data corruption and maybe even crash your system.
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If you are unsure, say N here.
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config USB_OTG
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bool
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depends on USB && EXPERIMENTAL
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@ -30,12 +30,6 @@
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#include "hcd.h"
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#include "hub.h"
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#ifdef CONFIG_USB_PERSIST
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#define USB_PERSIST 1
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#else
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#define USB_PERSIST 0
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#endif
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/* if we are in debug mode, always announce new devices */
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#ifdef DEBUG
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#ifndef CONFIG_USB_ANNOUNCE_NEW_DEVICES
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@ -695,7 +689,7 @@ static void hub_restart(struct usb_hub *hub, int type)
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* turn off the various status changes to prevent
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* khubd from disconnecting it later.
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*/
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if (USB_PERSIST && udev->persist_enabled && status == 0 &&
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if (udev->persist_enabled && status == 0 &&
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!(portstatus & USB_PORT_STAT_ENABLE)) {
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if (portchange & USB_PORT_STAT_C_ENABLE)
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clear_port_feature(hub->hdev, port1,
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@ -1923,9 +1917,8 @@ static int finish_port_resume(struct usb_device *udev)
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* the host and the device is the same as it was when the device
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* suspended.
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*
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* If CONFIG_USB_PERSIST and @udev->reset_resume are both set then this
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* routine won't check that the port is still enabled. Furthermore,
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* if @udev->reset_resume is set then finish_port_resume() above will
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* If @udev->reset_resume is set then this routine won't check that the
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* port is still enabled. Furthermore, finish_port_resume() above will
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* reset @udev. The end result is that a broken power session can be
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* recovered and @udev will appear to persist across a loss of VBUS power.
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*
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@ -1937,8 +1930,8 @@ static int finish_port_resume(struct usb_device *udev)
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* to it will be lost. Using the USB_PERSIST facility, the device can be
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* made to appear as if it had not disconnected.
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*
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* This facility is inherently dangerous. Although usb_reset_device()
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* makes every effort to insure that the same device is present after the
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* This facility can be dangerous. Although usb_reset_device() makes
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* every effort to insure that the same device is present after the
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* reset as before, it cannot provide a 100% guarantee. Furthermore it's
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* quite possible for a device to remain unaltered but its media to be
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* changed. If the user replaces a flash memory card while the system is
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@ -1983,7 +1976,7 @@ int usb_port_resume(struct usb_device *udev)
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status = hub_port_status(hub, port1, &portstatus, &portchange);
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SuspendCleared:
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if (USB_PERSIST && udev->reset_resume)
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if (udev->reset_resume)
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want_flags = USB_PORT_STAT_POWER
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| USB_PORT_STAT_CONNECTION;
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else
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@ -2113,10 +2106,10 @@ static int hub_reset_resume(struct usb_interface *intf)
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*
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* The USB host controller driver calls this function when its root hub
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* is resumed and Vbus power has been interrupted or the controller
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* has been reset. The routine marks @rhdev as having lost power. When
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* the hub driver is resumed it will take notice; if CONFIG_USB_PERSIST
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* is enabled then it will carry out power-session recovery, otherwise
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* it will disconnect all the child devices.
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* has been reset. The routine marks @rhdev as having lost power.
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* When the hub driver is resumed it will take notice and carry out
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* power-session recovery for all the "USB-PERSIST"-enabled child devices;
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* the others will be disconnected.
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*/
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void usb_root_hub_lost_power(struct usb_device *rhdev)
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{
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@ -97,4 +97,16 @@ void usb_detect_quirks(struct usb_device *udev)
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if (udev->descriptor.bDeviceClass != USB_CLASS_HUB)
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udev->autosuspend_disabled = 1;
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#endif
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#ifdef CONFIG_PM
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/* Hubs are automatically enabled for USB-PERSIST */
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if (udev->descriptor.bDeviceClass == USB_CLASS_HUB)
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udev->persist_enabled = 1;
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#else
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/* In the absense of PM, we can safely enable USB-PERSIST
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* for all devices. It will affect things like hub resets
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* and EMF-related port disables.
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*/
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udev->persist_enabled = 1;
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#endif /* CONFIG_PM */
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}
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@ -180,11 +180,9 @@ show_urbnum(struct device *dev, struct device_attribute *attr, char *buf)
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static DEVICE_ATTR(urbnum, S_IRUGO, show_urbnum, NULL);
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#if defined(CONFIG_USB_PERSIST) || defined(CONFIG_USB_SUSPEND)
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static const char power_group[] = "power";
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#endif
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#ifdef CONFIG_PM
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#ifdef CONFIG_USB_PERSIST
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static const char power_group[] = "power";
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static ssize_t
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show_persist(struct device *dev, struct device_attribute *attr, char *buf)
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@ -222,9 +220,10 @@ static int add_persist_attributes(struct device *dev)
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if (is_usb_device(dev)) {
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struct usb_device *udev = to_usb_device(dev);
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/* Hubs are automatically enabled for USB_PERSIST */
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if (udev->descriptor.bDeviceClass == USB_CLASS_HUB)
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udev->persist_enabled = 1;
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/* Hubs are automatically enabled for USB_PERSIST,
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* no point in creating the attribute file.
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*/
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if (udev->descriptor.bDeviceClass != USB_CLASS_HUB)
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rc = sysfs_add_file_to_group(&dev->kobj,
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&dev_attr_persist.attr,
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power_group);
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@ -238,13 +237,12 @@ static void remove_persist_attributes(struct device *dev)
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&dev_attr_persist.attr,
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power_group);
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}
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#else
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#define add_persist_attributes(dev) 0
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#define remove_persist_attributes(dev) do {} while (0)
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#endif /* CONFIG_USB_PERSIST */
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#endif /* CONFIG_PM */
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#ifdef CONFIG_USB_SUSPEND
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@ -28,7 +28,7 @@
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/*-------------------------------------------------------------------------*/
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#ifdef CONFIG_USB_PERSIST
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#ifdef CONFIG_PM
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static int ehci_hub_control(
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struct usb_hcd *hcd,
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@ -104,15 +104,6 @@ static void ehci_handover_companion_ports(struct ehci_hcd *ehci)
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ehci->owned_ports = 0;
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}
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#else /* CONFIG_USB_PERSIST */
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static inline void ehci_handover_companion_ports(struct ehci_hcd *ehci)
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{ }
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#endif
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#ifdef CONFIG_PM
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static int ehci_bus_suspend (struct usb_hcd *hcd)
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{
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struct ehci_hcd *ehci = hcd_to_ehci (hcd);
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@ -387,6 +387,7 @@ struct usb_device {
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unsigned can_submit:1; /* URBs may be submitted */
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unsigned discon_suspended:1; /* Disconnected while suspended */
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unsigned persist_enabled:1; /* USB_PERSIST enabled for this dev */
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unsigned have_langid:1; /* whether string_langid is valid */
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unsigned authorized:1; /* Policy has said we can use it */
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unsigned wusb:1; /* Device is Wireless USB */
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@ -433,7 +434,6 @@ struct usb_device {
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unsigned auto_pm:1; /* autosuspend/resume in progress */
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unsigned do_remote_wakeup:1; /* remote wakeup should be enabled */
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unsigned reset_resume:1; /* needs reset instead of resume */
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unsigned persist_enabled:1; /* USB_PERSIST enabled for this dev */
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unsigned autosuspend_disabled:1; /* autosuspend and autoresume */
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unsigned autoresume_disabled:1; /* disabled by the user */
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unsigned skip_sys_resume:1; /* skip the next system resume */
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