On Thu, 17 May 2018, Alexander Kappner wrote:

> Oliver and Alan,
> thank for investigating.
> > this is suspicious. You do not actually whether US_FL_NO_WP_DETECT
> > by itself would make the device work. Can you please test that?
> US_FL_NO_WP_DETECT without US_FL_IGNORE_UAS does not make a difference, 
> even with the patch you included applied:

Are you certain Oliver's new code was executed?  If you put 
US_FL_NO_WP_DETECT only in unusual_devs.h and not in ususual_uas.h then 
it would not affect the uas driver.

> > That's bizarre too.  Even though the only difference is a MODE SENSE 
> > command, the command that actually faliled was WRITE(16).
> It looks to me like the MODE SENSE simply hangs the drive, so anything 
> issued after that will fail. Of course the drive says it's the "current 
> command" that caused the failure, but I wouldn't give too much credence to 
> that. FYI -- this device is a consumer grade rotational drive that you can 
> get for less than $200, so I wouldn't be surprised if the implementations 
> have issues. 
> Also, I noticed that copying onto the drive with dd works fine, whereas 
> trying to mount a filesystem immediately crashes it. I suspect this is 
> because check_disk_change is called on mount (which eventually calls down 
> to sd_read_write_protect_flag, which is where the US_FL_NO_WP_DETECT flag 
> comes into play).

Was this tested with uas or usb-storage?

Alan Stern

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