Re: RFC: Platform data for onboard USB assets

Alan Stern
2011-03-11T16:45:22Z

On Fri, 11 Mar 2011, Andy Green wrote:

> > Like I say, it's not just MAC addresses that can need configuring this
> > way - it can be other random "you're wired up this way" type
> > information that would normally be figured out from the USB IDs.
>
> Yes that's exactly why I was thinking it's a class of requirement that
> could reasonably be a little API and extending platform_data to it. So
> anyone with onboard USB device can take advantage if they need to,
> because I guess we see gradually more boards like that.
>
> The driver knows well all about the actual device, but there is a class
> of configuration information that is defined by the physical board
> itself - as you say "how it is wired" - and needs to be passed into the
> driver to inform it of its "functional configuration". When that
> functional configuration information is a feature of the board alone,
> actually the board definition file is the right place for it.

I don't see the point of doing this for USB devices, or hot-pluggable
devices in general.

Suppose you bought another USB device that was just like the on-board
one, and plugged it into the system. Why should the driver need to
treat the on-board device any different from the hot-plugged device?

Or to put it another way... With external, hot-plugged USB devices,
there is no need to know "how it is wired". The fact that it is on a
USB bus is the only information necessary. Why does anyone need to
know more than this for on-board USB devices?

Alan Stern