On Fri, 18 May 2018, Alexander Kappner wrote: > Further debugging shows that the code that causes the device to hang is in > drivers/scsi/sd.c:2698. So the reason why usb-storage works and UAS does > not is because the device setting both skip_ms_page_3f=1 and > skip_ms_page_8=1 is required. The US_FL_NO_WP_DETECT flag does the former, > and usb-storage (but not UAS) by default does the latter > (drivers/usb/storage/scsiglue.c:198): > > /* > * A number of devices have problems with MODE SENSE for > * page x08, so we will skip it. > */ > sdev->skip_ms_page_8 = 1; > > > Forcing both skip_ms_page_3f and skip_ms_page_8 to 1 results in UAS and > usb-storage working. Oliver's code only set skip_ms_page_3f.
Good detective work! > Do we want a patch to introduce a quirk flag for skip_ms_page_8, similar to > the US_FL_NO_WP_DETECT quirk bit for skip_ms_page_3f? This may even resolve > the issues with other devices in unusual_uas.h that currently have all UAS > support disabled. I'd be happy to write the patch, but I'm not sure we want > to reserve a quirk bit for what's currently only a single device known to > have this issue. Please advise. Yes, I think we want a patch. Unless Oliver disagrees, please go ahead and prepare one. Alan Stern
