usb: Make USB persist default configurable
Commit 9214d1d8 set the USB persist flag as a default for all devices.
This might be desirable for some distributions, but it certainly has its
trade-offs... most importantly, it can significantly increase system
resume time, because the kernel blocks on resuming (and sometimes
resetting) USB devices before it unfreezes userspace.
This patch introduces a new config option CONFIG_USB_DEFAULT_PERSIST,
which allows distributions to make this decision on their own without
the need to carry a custom patch or revert the kernel's setting in
userspace.
[edited the Kconfig help text a bit - gregkh]
Signed-off-by: Julius Werner <jwerner@chromium.org>
Cc: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
diff --git a/drivers/usb/core/Kconfig b/drivers/usb/core/Kconfig
index 175701a..7b7305e 100644
--- a/drivers/usb/core/Kconfig
+++ b/drivers/usb/core/Kconfig
@@ -27,6 +27,22 @@
comment "Miscellaneous USB options"
depends on USB
+config USB_DEFAULT_PERSIST
+ bool "Enable USB persist by default"
+ depends on USB
+ default y
+ help
+ Say N here if you don't want USB power session persistance
+ enabled by default. If you say N it will make suspended USB
+ devices that lose power get reenumerated as if they had been
+ unplugged, causing any mounted filesystems to be lost. The
+ persist feature can still be enabled for individual devices
+ through the power/persist sysfs node. See
+ Documentation/usb/persist.txt for more info.
+
+ If you have any questions about this, say Y here, only say N
+ if you know exactly what you are doing.
+
config USB_DYNAMIC_MINORS
bool "Dynamic USB minor allocation"
depends on USB
diff --git a/drivers/usb/core/quirks.c b/drivers/usb/core/quirks.c
index 3113c1d..ab5638d 100644
--- a/drivers/usb/core/quirks.c
+++ b/drivers/usb/core/quirks.c
@@ -201,20 +201,14 @@
dev_dbg(&udev->dev, "USB quirks for this device: %x\n",
udev->quirks);
- /* For the present, all devices default to USB-PERSIST enabled */
-#if 0 /* was: #ifdef CONFIG_PM */
+#ifdef CONFIG_USB_DEFAULT_PERSIST
+ if (!(udev->quirks & USB_QUIRK_RESET))
+ udev->persist_enabled = 1;
+#else
/* Hubs are automatically enabled for USB-PERSIST */
if (udev->descriptor.bDeviceClass == USB_CLASS_HUB)
udev->persist_enabled = 1;
-
-#else
- /* In the absence of PM, we can safely enable USB-PERSIST
- * for all devices. It will affect things like hub resets
- * and EMF-related port disables.
- */
- if (!(udev->quirks & USB_QUIRK_RESET))
- udev->persist_enabled = 1;
-#endif /* CONFIG_PM */
+#endif /* CONFIG_USB_DEFAULT_PERSIST */
}
void usb_detect_interface_quirks(struct usb_device *udev)