Dear Jim Shimer,
While tuning ext2load, we found that usb_test_unit_ready was being called every block read. We compared the usb block storage to the scsi block storage cmd_scsi.c, and found that the scsi device was only calling its scsi_setup_test_unit_ready() during scsi_can. It appears that usb_test_unit_ready() really only needs to be called once during usb_stor_scan(), via usb_stor_get_info(). Is there a particular reason usb_test_unit_ready is called for every block read, or do you think its ok to only call during usb_stor_scan()? We're finding this speeds up ext2load quite a bit.
Could it be because the USB is actually quite slower than SCSI and the device might get congested? It seems the code was there ever since (I can't seem to find the origin of it) and we might actually want to try if this doesn't break some usb 1.x things.
Regards, Jim
Best regards, Marek Vasut