Re: [PATCH] Fix gadget serial response on USB_CDC_REQ_SET_LINE_CODING

> -----Original Message-----
> From: David Brownell [mailto:[email protected]]
> Sent: Monday, March 19, 2007 3:03 PM
> To: Li Yang-r58472
> Cc: [email protected]; [email protected]
> Subject: Re: [linux-usb-devel] [PATCH] Fix gadget serial response on
> USB_CDC_REQ_SET_LINE_CODING
> 
> On Sunday 18 March 2007 8:16 pm, Li Yang-r58472 wrote:
> > > -----Original Message-----
> > > From: David Brownell [mailto:[email protected]]
> > > Sent: Saturday, March 17, 2007 6:38 AM
> > > To: [email protected]
> > > Cc: Li Yang-r58472; [email protected]
> > > Subject: Re: [linux-usb-devel] [PATCH] Fix gadget serial response
on
> > > USB_CDC_REQ_SET_LINE_CODING
> > >
> > > On Wednesday 14 March 2007 5:18 am, Li Yang wrote:
> > > > Apparently this gadget doesn't support setting
usb_cdc_line_coding.
> > >
> > > It does support it ... but that support is buggy.  It should be
> > issuing
> > > a read request before doing the memcpy(); instead, it wrongly
assumes
> > > that something else already issued the read.
> >
> > Memcpy() the line_coding from host to the private port_line_coding
> > structure doesn't mean the port is really changed.  Port_line_coding
> > structure isn't used anywhere in the driver accept it fools around
the
> > next USB_CDC_REQ_GET_LINE_CODING request from host.
> 
> So if it's not used ... in what sense is the port *NOT* changed?
> 
> Remember, it's not hooked up to a serial line right now.  And other
> than asking for 8N1 (etc) "coding", that would be the only way to
> observe changes.
> 
> That is, if the memcpy were done *correctly* there would be no way
> to demonstrate what you're claiming.  Because every testable behavior
> would show the opposite.

Sorry for my ignorance.  So the parity and stop bits are never
transmitted on the USB line?  The line coding is only useful when there
is a down stream serial line?

As gadget serial doesn't support such down stream serial line.  Will be
it better to remove the SET_LINE_CODING, GET_LINE_CODING and
SET_CONTROL_LINE_STATE support?  Which also corresponds to the
bmCapabilities=0 in descriptor?

- Leo

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