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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All,

> > Can you try adding delays before, after, and inbetween the calls to 
> > sd_read_capacity, sd_read_write_protect_flag, and 
> sd_read_cache_type, 
> > all near the end of sd_revalidate_disk?
> 
> Yes, will do this and post results.

OK, it turns out that for this particular key, a two second pause after
"sd_spinup_disk" is called and before "sd_read_capacity" will make it work.
The 'dmesg' (or syslog) output is still ugly, however; but once I realised
that it was "sd_spinup_disk" that:

A) needed the delay, and 
B) causes the first ugly message to be printed in the first place, then a
better patch came to mind.

So, after combining Alan's suggestion to use "msleep" rather than my
previous convoluted method, and moving the location of the pause to inside
sd_spinup_disk (and targeting it to remove the first "ugly"), I came up with
a better patch, which is attached.

This patch adds the module parameter 'firmware_delay', and will cause a
pause for "firmware_delay" seconds inside sd_spinup_disk when the first SCSI
command returns UNIT_ATTENTION as the sense key.

Again, I have deliberately made the default value for this parameter 0,
which means that the end-user will need to ensure insmod or modprobe
supplies a >0 value to firmware_delay before the patch takes effect.

I'm not sure what the procedure is for getting this patch officially
recognised for inclusion into the kernel - Alan, are you able to "sponsor"
this patch for inclusion?

Thanks,

James Roberts-Thomson
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[-- Attachment #2: oti-usb-key-v2.patch --]
[-- Type: application/octet-stream, Size: 1119 bytes --]

--- /home/n202042/src/kernel2612/linux-2.6.12/drivers/scsi/sd.c	2005-06-18 07:48:29.000000000 +1200
+++ /usr/src/linux/drivers/scsi/sd.c	2005-07-11 15:40:45.000000000 +1200
@@ -89,6 +89,10 @@
 #define SD_MAX_RETRIES		5
 #define SD_PASSTHROUGH_RETRIES	1
 
+static unsigned int firmware_delay = 0;
+module_param(firmware_delay, uint, S_IRUGO | S_IWUSR);
+MODULE_PARM_DESC(firmware_delay, "Optional number of seconds delay for dodgy USB keys to settle");
+
 static void scsi_disk_release(struct kref *kref);
 
 struct scsi_disk {
@@ -1080,6 +1084,12 @@ sd_spinup_disk(struct scsi_disk *sdkp, c
 			/* Wait 1 second for next try */
 			msleep(1000);
 			printk(".");
+		} else if (sense_valid && sshdr.sense_key == UNIT_ATTENTION && firmware_delay > 0 ) {
+				/* Some USB flash drives need a small delay (perhaps to allow internal firmware
+				 * time to initialise
+				 */
+				printk(KERN_NOTICE "%s: Allowing time for firmware initialisation\n", diskname);
+				msleep(firmware_delay * HZ);
 		} else {
 			/* we don't understand the sense code, so it's
 			 * probably pointless to loop */