Subject: Re: UIO / of_genirq driver

From: Wolfram Sang <[email-masked]>
Date: Thu, 28 Jan 2010 11:45:45 +0100

John,

> I came across this thread/patchset from around June last year:
> 
> http://lists.ozlabs.org/pipermail/linuxppc-dev/2009-June/073086.html
> 
> where Wolfgang proposed a generic OF-driven UIO driver.  The

Wolfram, please ;)

> discussion seemed to stall after Grant Likely indicated he didn't like
> the use of a linux-specific compatible binding in the device tree
> (compatible="generic-uio").

I agree with him on that.

> I guess I have a couple of questions:
> 
>  * did this patchset go anywhere?  I've been using it here the last
> few days and it works great.

The idea was to create a mechanism to instantiate bindings at runtime, similar
to new_id for PCI/PCMCIA, e.g.:

$ echo "commodore,c64" > /sys/bus/of_platform/drivers/of_uio_genirq/new_compatible

so we don't have to maintain an ever growing list of hardcoded
compatible-properties for those UIO-devices.

>  * Is there a better way to handle the OF bindings for this sort of thing?

Run-time instantiation might help in a couple of other cases; still, in the
progress of unifying/extending the OF-support, it was discussed if it was
possible to get rid of of_platform entirely. It looks like a very challenging
task, but seems to be favoured designwise (at least I do).

> However, the device-tree guys complain whenever anyone tries to encode
> anything non-hardware related into the DTS itself.

Well, if I get a device tree including special properties for Linux and BSD and
whatever may follow, that could get quite confusing :)

> I guess I'd like to just open up a discussion, see if there's been any
> progress towards a general solution.

I decided to wait for the outcome of the of_platform-removal-idea. Though, I
have to admit that in the last weeks I haven't followed of-related things due
to other commitments.

Regards,

   Wolfram

-- 
Pengutronix e.K.                           | Wolfram Sang                |
Industrial Linux Solutions                 | http://www.pengutronix.de/  |