RE: [linux-usb-devel] Kernel unable to read partition table on US B Memory Key

["Roberts-Thomson, James" <James.Roberts-Thomson@NBNZ.CO.NZ>]

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Alan,
 
> Try putting delays at various spots in sd_revalidate_disk: 
> the beginning, the middle, and the end.

OK, the attached patch works for me when sd_mod was loaded with delay_use=1.

Now I'm quite prepared to be told that this is a really horrible and
inapproprate hack (given that I am not a kernel developer, I don't really
know the "correct" way to solve this problem); and I'll cheerfully admit
that it doesn't really solve the problem cleanly as can be seen below:

Jul  6 14:44:50 pc196344 kernel: usb 1-6: new high speed USB device using
ehci_hcd and address 6
Jul  6 14:44:50 pc196344 kernel: Initializing USB Mass Storage driver...
Jul  6 14:44:50 pc196344 kernel: scsi5 : SCSI emulation for USB Mass Storage
devices
Jul  6 14:44:50 pc196344 kernel: usbcore: registered new driver usb-storage
Jul  6 14:44:50 pc196344 kernel: USB Mass Storage support registered.
Jul  6 14:44:50 pc196344 kernel: usb-storage: device found at 6
Jul  6 14:44:50 pc196344 kernel: usb-storage: waiting for device to settle
before scanning
Jul  6 14:44:52 pc196344 kernel:   Vendor: OTi       Model: Flash Disk
Rev: 2.00
Jul  6 14:44:52 pc196344 kernel:   Type:   Direct-Access
ANSI SCSI revision: 02
Jul  6 14:44:52 pc196344 kernel: Attached scsi generic sg1 at scsi5, channel
0, id 0, lun 0,  type 0
Jul  6 14:44:52 pc196344 kernel: usb-storage: device scan complete
Jul  6 14:44:52 pc196344 scsi.agent[27245]: disk at
/devices/pci0000:00/0000:00:1d.7/usb1/1-6/1-6:1.0/host5/target5:0:0/5:0:0:0
Jul  6 14:44:52 pc196344 kernel: sd: waiting for device to get ready.
Jul  6 14:44:53 pc196344 kernel: sda: Unit Not Ready, sense:
Jul  6 14:44:53 pc196344 kernel: : Current: sense key: Unit Attention
Jul  6 14:44:53 pc196344 kernel:     Additional sense: Not ready to ready
change, medium may have changed
Jul  6 14:44:53 pc196344 kernel: sda : READ CAPACITY failed.
Jul  6 14:44:53 pc196344 kernel: sda : status=1, message=00, host=0,
driver=08
Jul  6 14:44:53 pc196344 kernel: sd: Current: sense key: Unit Attention
Jul  6 14:44:53 pc196344 kernel:     Additional sense: Not ready to ready
change, medium may have changed
Jul  6 14:44:53 pc196344 kernel: sda: test WP failed, assume Write Enabled
Jul  6 14:44:53 pc196344 kernel: sda: assuming drive cache: write through
Jul  6 14:44:53 pc196344 kernel: sd: waiting for device to get ready.
Jul  6 14:44:54 pc196344 kernel: sda: Unit Not Ready, sense:
Jul  6 14:44:54 pc196344 kernel: : Current: sense key: Unit Attention
Jul  6 14:44:54 pc196344 kernel:     Additional sense: Not ready to ready
change, medium may have changed
Jul  6 14:44:54 pc196344 kernel: sda : READ CAPACITY failed.
Jul  6 14:44:54 pc196344 kernel: sda : status=1, message=00, host=0,
driver=08
Jul  6 14:44:54 pc196344 kernel: sd: Current: sense key: Unit Attention
Jul  6 14:44:54 pc196344 kernel:     Additional sense: Not ready to ready
change, medium may have changed
Jul  6 14:44:54 pc196344 kernel: sda: test WP failed, assume Write Enabled
Jul  6 14:44:54 pc196344 kernel: sda: assuming drive cache: write through
Jul  6 14:44:54 pc196344 kernel: sd: waiting for device to get ready.
Jul  6 14:44:55 pc196344 kernel: SCSI device sda: 255488 512-byte hdwr
sectors (131 MB)
Jul  6 14:44:55 pc196344 kernel: sda: Write Protect is off
Jul  6 14:44:55 pc196344 kernel: sda: Mode Sense: 03 00 00 00
Jul  6 14:44:55 pc196344 kernel: sda: assuming drive cache: write through
Jul  6 14:44:55 pc196344 kernel:  /dev/scsi/host5/bus0/target0/lun0: p1
Jul  6 14:44:55 pc196344 kernel: Attached scsi removable disk sda at scsi5,
channel 0, id 0, lun 0

There are three delays from my patch in the above list, and increasing the
delay to 3 seconds didn't help, as I got three one-second delays.  

However, if someone with the appropriate knowledge could transform my kludge
into a proper fix, then I would be very happy.

Alan, thanks very much for your help - I really appreciate the quick
responses you have given me.

Note that I now have the output from the USB Snoop tool under Windows if
anyone wants it - please ask if needed to help solve the issue "correctly".

James Roberts-Thomson
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[-- Attachment #2: oti-usb-key.patch --]
[-- Type: application/octet-stream, Size: 947 bytes --]

--- linux-2.6.12/drivers/scsi/sd.c	2005-06-18 07:48:29.000000000 +1200
+++ linux-2.6.12-jrt1/drivers/scsi/sd.c	2005-07-06 14:33:27.000000000 +1200
@@ -89,6 +89,10 @@
 #define SD_MAX_RETRIES		5
 #define SD_PASSTHROUGH_RETRIES	1
 
+static unsigned int delay_use = 0;
+module_param(delay_use, uint, S_IRUGO | S_IWUSR);
+MODULE_PARM_DESC(delay_use, "Optional number of seconds delay for dodgy USB keys to settle");
+
 static void scsi_disk_release(struct kref *kref);
 
 struct scsi_disk {
@@ -1483,6 +1487,14 @@ static int sd_revalidate_disk(struct gen
 	sdkp->WCE = 0;
 	sdkp->RCD = 0;
 
+	/* Wait for the timeout to expire */
+	if (delay_use > 0) {
+		printk(KERN_DEBUG "sd: waiting for device to get ready.\n");
+		wait_queue_head_t delay_wait;
+		init_waitqueue_head(&delay_wait);
+		wait_event_interruptible_timeout(delay_wait, 0, delay_use * HZ);
+	}
+	
 	sd_spinup_disk(sdkp, disk->disk_name, sreq, buffer);
 
 	/*