linux-kernel - Re: [PATCH] usb host: Faraday FUSBH200 HCD driver.

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Date:	Mon, 18 Mar 2013 10:16:56 -0400 (EDT)
From:	Alan Stern <stern@...land.harvard.edu>
To:	Felipe Balbi <balbi@...com>
cc:	Yuan-Hsin Chen <yuanlmm@...il.com>, <gregkh@...uxfoundation.org>,
	<sarah.a.sharp@...ux.intel.com>, <Julia.Lawall@...6.fr>,
	<linux-usb@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	Yuan-Hsin Chen <yhchen@...aday-tech.com>,
	<john453@...aday-tech.com>
Subject: Re: [PATCH] usb host: Faraday FUSBH200 HCD driver.

On Mon, 18 Mar 2013, Felipe Balbi wrote:

> On Mon, Mar 18, 2013 at 06:06:18PM +0800, Yuan-Hsin Chen wrote:
> > Hi,
> > 
> > I tried to modify fusbh200 hcd driver following ehci-platform.c.
> > However, the register definition of fusbh200 is partially incompatible
> > to ehci. For fusbh200, only the elements between "command" and
> > "async_next" in struct ehci_regs are consistent with ehci which means

What about the port_status registers?  They're not between command and
async_next.  If they aren't consistent with EHCI, it makes things a lot
more complicated.

> > it would cause copious modification and duplication of ehci hcd
> > driver. For example, there is no "configured_flag" register in
> > fusbh200 controller, yet, ehci hcd driver accesses "configured_flag"
> > in function ehci_run which would cause compile errors. Therefore,
> > maybe my first patch which refers to oxu210hp-hcd is a better
> > solution?
> 
> why don't you just add a quirk flag to ehci struct so that it knows it
> shouldn't access CONFIGFLAG register when that's non-existent ?
> 
> There are only 5 uses of configured_flag in ehci-hcd.c, so it should be
> easy to wrap that around a flag check.

Two of those uses turn configured_flag on and two of them turn it off.  
However, one of the uses tests its value (the first one in
ehci_resume).  How would that be handled if configured_flag doesn't
exist?

> Alan, would you have a better idea ? Looks like this is a non-standard
> EHCI implementation.

Yes, it does.  If all we need is to protect four or five accesses with 
a quirk flag, that's okay with me.

Alan Stern

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