linux-kernel - Re: RFC: Platform data for onboard USB assets

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Date:	Thu, 17 Mar 2011 14:47:36 -0700
From:	Greg KH <greg@...ah.com>
To:	Mark Brown <broonie@...nsource.wolfsonmicro.com>
Cc:	Nicolas Pitre <nicolas.pitre@...aro.org>,
	Arnd Bergmann <arnd@...db.de>, andy.green@...aro.org,
	Linux USB list <linux-usb@...r.kernel.org>,
	lkml <linux-kernel@...r.kernel.org>
Subject: Re: RFC: Platform data for onboard USB assets

On Thu, Mar 17, 2011 at 09:40:42PM +0000, Mark Brown wrote:
> On Thu, Mar 17, 2011 at 02:31:08PM -0700, Greg KH wrote:
> > On Thu, Mar 17, 2011 at 09:24:49PM +0000, Mark Brown wrote:
> 
> > > The way this is normally done is that the ethernet controller can be
> > > attached to a SEPROM which it reads when it powers on.  This will
> > > contain a number of device configuration parameters, including the
> > > vendor IDs and the MAC address, which will be configured before the
> > > device makes itself available on the bus.  If the system integrator has
> > > omitted the SEPROM then the device will come up with defaults, usually
> > > something like all zeros.
> 
> > Ok, then again, let's deal with this on a case-by-case basis please, as
> > this is going to be a "rare" thing in the real world.  I don't want to
> > encourage _any_ engineers to think that this is ok to do for USB
> > devices.
> 
> It's really not at all rare in the embedded world - the overwhelming
> majority of the systems I've worked on have omitted the SEPROMS for
> components that are soldered down in the system.  It'd be pretty insane
> to do it for things that are distinct USB devices but that's not the
> case.
> 
> There are good solid engineering reasons for doing things this way if
> you've got any prospect of shifting any kind of volume, as well as the
> cost saving achieved by removing a component you also simplify and most
> likely speed up the production process as you can reduce the number of
> components that need to be programmed on each system that gets built.
> 
> > Patches to fix this, for this specific PandaBoard controller are gladly
> > accepted.  What's odd is this is explicitly a Linux development board,
> > so you would think that this could have been caught, and fixed, in the
> > hardware a long time ago, right?
> 
> The way everyone resolves this stuff is by patching their kernel
> locally.

Well, that means that the device tree work is going to be useful here,
right?  :)

Best of luck,

greg k-h
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