Oliver Neukum schrieb:
as we discussed earlier devices which need to be switched must
not be reset. Currently I think only the storage driver is affected.
The serial drivers (generic, "option", cdc_acm) are affected as well.
These (plus any storage parts visible after switching) are the
"target" devices created by the mode switching and thus "unstable"
(meaning they may be lost during a reset).
Ideally we would not put all those devices into the quirks list.
I'd prefer the user space tools making the switch to tell the kernel
that the new device is quirky.
What kind of API for that would you prefer?
For simplicity's sake I'd like a writable sysfs flag in the way of
/sys/bus/usb/devices/<device address>/no_reset (0/1)
or similar ("no_resetresume" ?). I'm free of any knowledge about
naming and folder conventions though, so no preference there.
Josh
From ff39d073bda410d032d17711a7deb1761f451bae Mon Sep 17 00:00:00 2001
From: Oliver Neukum <oliver@xxxxxxxxxx>
Date: Mon, 14 Dec 2009 17:59:11 +0100
Subject: [PATCH] usb-storage:Never reset devices that will morph to an old mode
Some devices must be switched to a new mode to fully use them.
A reset would make them revert to the old mode. Therefore a reset
must not be used for error handling with such devices.
Signed-off-by: Oliver Neukum <oliver@xxxxxxxxxx>
---
drivers/usb/core/quirks.c | 3 ++-
drivers/usb/storage/transport.c | 6 ++++++
include/linux/usb/quirks.h | 3 +++
3 files changed, 11 insertions(+), 1 deletions(-)
diff --git a/drivers/usb/core/quirks.c b/drivers/usb/core/quirks.c
index ab93918..0b68922 100644
--- a/drivers/usb/core/quirks.c
+++ b/drivers/usb/core/quirks.c
@@ -120,6 +120,7 @@ void usb_detect_quirks(struct usb_device *udev)
* for all devices. It will affect things like hub resets
* and EMF-related port disables.
*/
- udev->persist_enabled = 1;
+ if (!(udev->quirks & USB_QUIRK_RESET_MORPHS))
+ udev->persist_enabled = 1;
#endif /* CONFIG_PM */
}
diff --git a/drivers/usb/storage/transport.c b/drivers/usb/storage/transport.c
index cc313d1..4680381 100644
--- a/drivers/usb/storage/transport.c
+++ b/drivers/usb/storage/transport.c
@@ -47,6 +47,8 @@
#include <linux/errno.h>
#include <linux/slab.h>
+#include <linux/usb/quirks.h>
+
#include <scsi/scsi.h>
#include <scsi/scsi_eh.h>
#include <scsi/scsi_device.h>
@@ -1297,6 +1299,10 @@ int usb_stor_port_reset(struct us_data *us)
{
int result;
+ /*for these devices we must use the class specific method */
+ if (us->pusb_dev->quirks & USB_QUIRK_RESET_MORPHS)
+ return -EPERM;
+
result = usb_lock_device_for_reset(us->pusb_dev, us->pusb_intf);
if (result < 0)
US_DEBUGP("unable to lock device for reset: %d\n", result);
diff --git a/include/linux/usb/quirks.h b/include/linux/usb/quirks.h
index 2526f3b..0a555dd 100644
--- a/include/linux/usb/quirks.h
+++ b/include/linux/usb/quirks.h
@@ -19,4 +19,7 @@
/* device can't handle its Configuration or Interface strings */
#define USB_QUIRK_CONFIG_INTF_STRINGS 0x00000008
+/*device will morph if reset, don't use reset for handling errors */
+#define USB_QUIRK_RESET_MORPHS 0x00000010
+
#endif /* __LINUX_USB_QUIRKS_H */
--
Man is the only creature on earth enabled to take a
warm meal while flying! Loriot
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