Re: CP210x Driver - Issue Enumerating Multiple Interfaces

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On Fri, May 16, 2014 at 05:54:12AM -0400, Miner, Blake wrote:
> > I am not sure about this, but I wonder can we do the reset in
> > cp210x_open() instead of in cp210x_startup()?
> 
> Possibly, but I'd rather perform the reset just once, right when the
> device is detected and bound to the driver.  After doing some more
> reading, I've found that calling `usb_lock_device_for_reset` just
> before `usb_reset_device` seems to work.  Here's a possible patch:
> 
> --- cp210x.c
> +++ cp210x.c.new.c
> @@ -856,7 +856,8 @@
>   struct cp210x_serial_private *spriv;
> 
>   /* cp210x buffers behave strangely unless device is reset */
> - usb_reset_device(serial->dev);
> + if(usb_lock_device_for_reset(serial->dev, NULL) == 0)
> + usb_reset_device(serial->dev);
> 
>   spriv = kzalloc(sizeof(*spriv), GFP_KERNEL);
>   if (!spriv)
> 
> The downside here is that the reset takes a few hundred extra
> milliseconds, and the reset is issued for each interface.  But, at
> least both interfaces are properly detected the first time.  :)  Any
> thoughts?

That seems resonable.  Care to make it into a patch that we can apply to
the tree (read Documentation/SubmittingPatches for all of the details.)

thanks,

greg k-h
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