Re: Linux USB file storage gadget with new UDC

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On Fri, 15 Mar 2013, Felipe Balbi wrote:

> On Fri, Mar 15, 2013 at 04:26:10PM +0800, victor yeo wrote:
> > Hi,
> > 
> > > On Fri, Mar 15, 2013 at 01:59:30PM +0800, victor yeo wrote:
> > >> For bulk transfer, the new UDC driver has one problem. When SCSI
> > >> Inquiry command is received, the UDC driver interrupt routine will
> > >> receive it first. However, the queue function is not yet called, and
> > >> queue buffer is not yet added. Thus, interrupt routine is not able to
> > >> store the SCSI Inquiry command to the queue buffer.
> > >>
> > >> This is a serious problem, what is the way to synchronise UDC driver
> > >> and file storage gadget driver for SCSI command bulk transfer?
> > >
> > > don't process the interrupt until you receive a queue. Data will be
> > > pending in controller's FIFO until then.
> > >
> > 
> > change to do exactly that, bulk transfer interrupt come in, don't
> > process, then queue function is called to add  queue buffer. After
> > that, no more bulk transfer interrupt come in.
> 
> did you process the pending data from FIFO after queue was called ?

I'm not sure about the details of how the controller hardware works.  
But what should happen is this: When the controller receives the bulk 
packet containing the INQUIRY command, it should send back NAK until it 
has a buffer ready to store the packet.

Alan Stern

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