Re: how mass storage device cope with unsupported commands?

[Alan Stern <stern@xxxxxxxxxxxxxxxxxxx>]

On Thu, 29 Jun 2006, JackRain wrote:

> 		  because I write the device usb firmware by myself,i print less message only for the software flow chart.
> 
> 		  now:
> 		   1)when device get READ_FORMAT_CAPCITY(0x23) command ,stall the bulk-in endpoint. 
>        	   2)waitting for ep0setup interrupt,and get the clear_feature request \
> 			 unstall the endpoint and toggle the DATA pid by disable then enable the bulk-in endpoint (isp1582)

You're supposed to set the data toggle to 0.  Maybe disabling and then
enabling the endpoint does that.

> 		   3)bulk-in endpoint send a ACK signal to PC;

This should not happen.  The bulk-in endpoint should not send an ACK,
since it has not received an IN pid.

> 		   4)then send the CSW to PC to reflect the command status of this unsupported command 

Okay.  Remember to set dCSWResidue = dCBWDataTransferLength.

> 		   5)EP0TX send a ACK signal to PC

This isn't right.  ep0 is supposed to send a 0-length packet to perform
the handshake stage of the control message.  Then the _host_ sends an ACK.

> 		   6) bus reset.
>            7)bulk-out endpoint interrypt occurs,read CBW 
> 		   if command unsupported ,do the same thing 1~5;
> 		
> 		   again bus reset.
> 
>            if command supported ,it's normal and go on processing SCSI protocol.
> 		   and I can't see the disk tray icon on windows.
> 		   but because bus reset ,the device still won't work.

Probably the bus resets occur because of the earlier protocol mistakes.

Alan Stern


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