Hi!
Here I have this patch ported from a 2.4 verison of a patch by guy at
Dell ([EMAIL PROTECTED]), that uses the serialize semaphore in devio.c
and in usb-storage.
This is needed on storage devices, where even sending a harmless
GET_DESCRIPTOR command at the wrong time will lead to a STALL condition,
and make the device unusable.
Because many a hotplug script does exactly that, it's rather easy to get
a non-working device.
I hope this use of the serialize semaphore is correct - at least it
looks OK to me.
diff -urN linux-2.6.5/drivers/usb/core/devio.c
linux-2.6.5-dell/drivers/usb/core/devio.c
--- linux-2.6.5/drivers/usb/core/devio.c 2004-05-20 15:05:10.000000000 +0200
+++ linux-2.6.5-dell/drivers/usb/core/devio.c 2004-05-20 15:13:33.000000000 +0200
@@ -1205,6 +1205,12 @@
up_read(&ps->devsem);
return -ENODEV;
}
+ /*
+ * grab device's serialize mutex to prevent driver from
+ * using this device while it is being accessed by us
+ */
+ down (&(ps->dev->serialize));
+
switch (cmd) {
case USBDEVFS_CONTROL:
ret = proc_control(ps, (void __user *)arg);
@@ -1284,6 +1290,7 @@
ret = proc_ioctl(ps, (void __user *) arg);
break;
}
+ up (&(ps->dev->serialize));
up_read(&ps->devsem);
if (ret >= 0)
inode->i_atime = CURRENT_TIME;
diff -urN linux-2.6.5/drivers/usb/storage/transport.c
linux-2.6.5-dell/drivers/usb/storage/transport.c
--- linux-2.6.5/drivers/usb/storage/transport.c 2004-05-20 15:05:08.000000000 +0200
+++ linux-2.6.5-dell/drivers/usb/storage/transport.c 2004-05-20 15:16:07.000000000
+0200
@@ -527,9 +527,18 @@
int need_auto_sense;
int result;
+ /*
+ * Grab device's serialize mutex to prevent /usbfs and others from
+ * sending out a command in the middle of ours (if libusb sends a
+ * get_descriptor or something on pipe 0 after our CBW and before
+ * our CSW, and then we get a stall, we have trouble)
+ */
+
/* send the command to the transport layer */
+ down (&(us->pusb_dev->serialize));
srb->resid = 0;
result = us->transport(srb, us);
+ up (&(us->pusb_dev->serialize));
/* if the command gets aborted by the higher layers, we need to
* short-circuit all other processing
@@ -648,9 +657,11 @@
srb->serial_number ^= 0x80000000;
/* issue the auto-sense command */
+ down (&(us->pusb_dev->serialize));
old_resid = srb->resid;
srb->resid = 0;
temp_result = us->transport(us->srb, us);
+ up (&(us->pusb_dev->serialize));
/* let's clean up right away */
srb->resid = old_resid;
--
Vojtech Pavlik
SuSE Labs, SuSE CR
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