Re: how mass storage device cope with unsupported commands?

[Alan Stern <stern@xxxxxxxxxxxxxxxxxxx>]

On Wed, 28 Jun 2006, JackRain wrote:

> linux-usb-users£¬ÄúºÃ£¡
> 
> 	      hi,glad to see you again:)
> 
> 		  i would like to ask a question about £º  how does mass storage device cope with unsupported commands,such as 0x23 etc?

Many mass storage devices do support that command.  It is documented in 
the UFI specification.

> 		  my way is :  refering to mass bulk-only spec.(usbmassbulk_10  6.6.4 command failure),
> 
> 	      The device shall report this condition by returning a Command Failed status (bCSWStatus = 01h).
> 
> 		  so,i now try :
> 
> 			   1) return with sense_data 6th,12th,13th: 0x5,0x24,0x00.

You can't return sense data to the host unless the command was REQUEST 
SENSE.

> 			   2) return CSW with status (0x01) fail.
> 
>           but it seems from bus hound that ,the USB commnication halt a long time then reset.

What mass storage device are you talking about?  Do you have any logs you 
can post?

> 		  another method i have tried is to stall the bulk-in endpoint then wait host __set feature__ and unstall endpoint.
> 	
> 		  this failed again~
> 
>           could anyone tell me the correct way ?? thank you very much~

According to the specification, you are supposed to stall the bulk-in
endpoint (if the Direction bit was set in bmCBWFlags; otherwise you should
stall the bulk-out endpoint) and then return CSW status = 1.  When the
host then sends a REQUEST SENSE command, you should reply with key = 0x5,
ASC = 0x24, ASCQ = 0x00.

Alan Stern


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