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authorJulius Werner <jwerner@chromium.org>2013-03-13 15:57:31 -0700
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2013-03-29 09:29:12 -0700
commit4f48203881ce947a0cbd8ae7b1a1a1b04aaa3766 (patch)
tree522224ae58cbe21d4468cffb2f54af31dd7b5094 /drivers
parent70b55c2ad0e5c8bbbb36cedf6a37f9d029cfd403 (diff)
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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>
Diffstat (limited to 'drivers')
-rw-r--r--drivers/usb/core/Kconfig16
-rw-r--r--drivers/usb/core/quirks.c16
2 files changed, 21 insertions, 11 deletions
diff --git a/drivers/usb/core/Kconfig b/drivers/usb/core/Kconfig
index 175701a2dae4..7b7305e3abc8 100644
--- a/drivers/usb/core/Kconfig
+++ b/drivers/usb/core/Kconfig
@@ -27,6 +27,22 @@ config USB_ANNOUNCE_NEW_DEVICES
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 3113c1d71442..ab5638d9c707 100644
--- a/drivers/usb/core/quirks.c
+++ b/drivers/usb/core/quirks.c
@@ -201,20 +201,14 @@ void usb_detect_quirks(struct usb_device *udev)
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 */
- /* Hubs are automatically enabled for USB-PERSIST */
- if (udev->descriptor.bDeviceClass == USB_CLASS_HUB)
+#ifdef CONFIG_USB_DEFAULT_PERSIST
+ if (!(udev->quirks & USB_QUIRK_RESET))
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))
+ /* Hubs are automatically enabled for USB-PERSIST */
+ if (udev->descriptor.bDeviceClass == USB_CLASS_HUB)
udev->persist_enabled = 1;
-#endif /* CONFIG_PM */
+#endif /* CONFIG_USB_DEFAULT_PERSIST */
}
void usb_detect_interface_quirks(struct usb_device *udev)