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

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Date:	Mon, 18 Mar 2013 14:47:17 -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:

> Hi,
> 
> On Mon, Mar 18, 2013 at 10:16:56AM -0400, Alan Stern wrote:
> > > > 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?
> 
> perhaps they don't use it because they have a root-hub TT ? In that case
> you assume EHCI *always* owns the port. Would that work ?

The usage in ehci_resume is meant for checking whether power was lost 
while the controller was suspended.  This probably isn't an issue 
during runtime suspend; it's likely to come up only during system 
suspend.  If Yuan-Hsin's platform doesn't support system suspend then 
we don't have to worry about it.

Alan Stern

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