On Fri, 2 Dec 2005, Timothy Thelin wrote: > Hi all, > > I have a USB bridge that's implementing SAT passthru cdbs. We ran into an > issue with the usb-storage driver in that when it does auto-sense (because > the CK_COND bit is set in the passthru cdb), the driver does a sense with > only 18 bytes for the sense buffer. The problem is that SAT passthru wants > to return 22 bytes of sense data. The last 4 bytes that don't get returned > are fairly important ATA task files registers: lba high hob, lba high, > device, and status. > > For testing purposes I use the patch below, but what's the correct way to > deal with this issue? Is there something in the USB spec mandating 18 bytes > of sense data, or is the usb-storage simply making a hard-coded assumption?
I believe it's a hard-coded assumption, based on the observation that many USB devices don't like it if you ask for more or less than 18 bytes. Matt Dharm can correct this if I'm wrong. The sense buffer length is yet another quantity that ought to have an SG passthru but doesn't. Your patch looks to me like a reasonable approach, given the constraints we are under. It would be nice to have a cleaner way of determining which commands need the extra sense data. Could you make that test into a separate subroutine? And perhaps use symbolic names for the command bytes. Alan Stern ------------------------------------------------------- This SF.net email is sponsored by: Splunk Inc. Do you grep through log files for problems? Stop! Download the new AJAX search engine that makes searching your log files as easy as surfing the web. DOWNLOAD SPLUNK! http://ads.osdn.com/?ad_id=7637&alloc_id=16865&op=click _______________________________________________ Linux-usb-users@lists.sourceforge.net To unsubscribe, use the last form field at: https://lists.sourceforge.net/lists/listinfo/linux-usb-users
