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.
Signed-off-by: Julius Werner <jwer...@chromium.org>
---
drivers/usb/core/Kconfig | 14 ++++++++++++++
drivers/usb/core/quirks.c | 16 +++++-----------
2 files changed, 19 insertions(+), 11 deletions(-)
diff --git a/drivers/usb/core/Kconfig b/drivers/usb/core/Kconfig
index f70c1a1..dfc1360 100644
--- a/drivers/usb/core/Kconfig
+++ b/drivers/usb/core/Kconfig
@@ -27,6 +27,20 @@ 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. This will make suspended USB devices that
+ lose power get reenumerated as if they had been unplugged,
+ but may reduce your system's resume time and eliminates any
+ chance of file system corruption by confusing two devices with
+ the same vendor and product ID. The persist feature can still
+ be enabled for individual devices through the power/persist
+ sysfs node. See Documentation/usb/persist.txt for more info.
+
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 @@ 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)
--
1.7.12.4
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