linux-kernel - Re: [PATCH v12 7/8] usb: Adding SuperSpeed support to dummy

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Date:	Wed, 25 May 2011 12:20:03 +0300
From:	Felipe Balbi <balbi@...com>
To:	Alan Stern <stern@...land.harvard.edu>
Cc:	Tanya Brokhman <tlinder@...eaurora.org>, balbi@...com,
	'Sarah Sharp' <sarah.a.sharp@...ux.intel.com>, greg@...ah.com,
	linux-usb@...r.kernel.org, linux-arm-msm@...r.kernel.org,
	ablay@...eaurora.org, 'open list' <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v12 7/8] usb: Adding SuperSpeed support to dummy_hcd

Hi,

On Tue, May 24, 2011 at 10:20:37AM -0400, Alan Stern wrote:
> On Tue, 24 May 2011, Tanya Brokhman wrote:
> 
> > Hi Felipe
> > 
> > > > Yes :) The driver->speed is updated in usb_composite_probe() if
> > > > CONFIG_USB_GADGET_SUPERSPEED is defined.
> > > >
> > > > So, are we ok with this solution? The module parameter I mean?
> > > > Are you going to try the v13 in your branch? Please let me know how
> > > it
> > > > goes and of course if you have any comments.
> > > 
> > > I think it still gives the possibility for failure. I would rather not
> > > take that until all gadget drivers are fixed. We can help you doing
> > > that and we only change driver->speed after all gadget drivers have
> > > their "sensible defaults" SuperSpeed descriptors.
> > 
> > By "until all gadget drivers are fixed" you mean until all gadget drivers
> > provide SS descriptors? This will take for ever... 
> > I wasn't about to modify all gadget drivers and to add SS descriptors for
> > them. I can add default values (as generate_ss_descriptors() did if you
> > remember) but I don't think this is the right approach because as you said -
> > different gadget drivers might have different SS descriptors and I don't
> > feel confident enough to set these values. Nor do I have the ability to test
> > each of the gadget drivers the way I would like to after this change.
> > The only gadget driver I felt confident adding SS descriptors for is UASP,
> > which I tested properly.
> > 
> > Actually if the CONFIG_USB_GADGET_SUPERSPEED is turned off, which is the
> > default of it, the speed won't be updated and all these series won't be
> > functional so I don't see any possibilities for failure in such
> > configuration. Or am I missing something?
> 
> dummy_hcd should work when CONFIG_USB_GADGET_SUPERSPEED is enabled,
> even if the usb_gadget_driver structure is initialized with the speed
> field set to USB_SPEED_HIGH.  This will be true for all the standalone
> gadget drivers until they are updated.
> 
> Which leaves a question about the composite gadget framework.  Should
> it be updated with SS support?  Probably not until the various function
> drivers have all been updated.

We can add support for all the USB3 standard requests, just don't change
the driver->speed field until all gadget drivers are fixed.

-- 
balbi

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