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RFC: Platform data for onboard USB assets

From:  Andy Green <andy-AT-warmcat.com>
To:  Linux USB list <linux-usb-AT-vger.kernel.org>
Subject:  RFC: Platform data for onboard USB assets
Date:  Fri, 11 Mar 2011 09:50:32 +0000
Message-ID:  <4D79F068.2080009@linaro.org>
Cc:  lkml <linux-kernel-AT-vger.kernel.org>
Archive-link:  Article

Hi -

platform_data is a well established way in Linux to pass configuration 
data up to on-board assets from a machine file like mach-xyz.c.  It's 
also supported to pass platform_data up to devices that are probed 
asynchronously from busses like i2c as well, which is very handy.

However AFAIK it's not possible to bind platform_data to probed USB 
devices as it stands.

There are now boards which have on-board USB assets, for example OMAP4 
Panda which has a USB <-> Ethernet bridge wired up permanently.  It'd be 
convenient to also be able to pass optional platform_data to these 
devices when they are asynchronously probed.

So what's the feeling about a new api to register an array of 
platform_data pointers bound to static "devpath" names in the machine file?

When a usb device is instantiated, it can check through this array if it 
exists, matching on devname, and attach the platform_data to the 
underlying probed usb device's dev->platform_data, which it seems is 
currently unused.

The particular use that suggested this is on Panda, it would be ideal to 
be able to set a flag in the usb device's platform data that forces it 
to be named eth%d since it's a hardwired asset on the board with an RJ45 
socket.

Comments, implementation suggestions, enquiries as to my level of crack 
consumption etc welcomed ^^

-Andy


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