linux-kernel - Re: [PATCH] usb: host: Faraday fotg210-hcd driver

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Date:	Tue, 18 Jun 2013 10:43:56 -0400 (EDT)
From:	Alan Stern <stern@...land.harvard.edu>
To:	Yuan-Hsin Chen <yuanlmm@...il.com>
cc:	Sarah Sharp <sarah.a.sharp@...ux.intel.com>,
	Greg KH <gregkh@...uxfoundation.org>,
	Yuan-Hsin Chen <yhchen@...aday-tech.com>,
	Felipe Balbi <balbi@...com>, <florian@...nwrt.org>,
	USB list <linux-usb@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>, ratbert <ratbert.chuang@...il.com>,
	John Feng-Hsin Chiang(江峰興) 
	<john453@...aday-tech.com>
Subject: Re: [PATCH] usb: host: Faraday fotg210-hcd driver

On Tue, 18 Jun 2013, Yuan-Hsin Chen wrote:

> > In that case, no, you should be figuring out how to refactor and reuse
> > the EHCI code instead of copying it straight into your driver.
> 
> I was trying to use ehci-platform.c, anonymous union/struct, and quirk
> flags to avoid copying EHCI code.
> But there are too big incompatibilities between fotg210/fusbh200
> controller and EHCI.
> That's why Alan agreed that I could create a stand-alone driver for
> fusbh200 host controller.
> Since fotg210 and fusbh200 have the same issue,  fotg210 hcd is
> supposed to be stand-alone.
> More details please refer to mail sequence
> http://www.spinics.net/lists/linux-usb/msg83812.html

That's right.  The patch's description mentions some of the
incompatibilities.  In short, the Faraday controllers are a _very_
noncompliant EHCI variant.  The changes needed to make ehci-hcd work
with them were too invasive IMO.

It's a shame, because so much of the code is the same.  It makes you 
want to go back and ask those Faraday engineers what they were thinking 
of at the time.

Alan Stern

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