netdev - Re: [RFC fs_enet: Convert MII bitbang driver to use GPIO lib

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Message-Id: <200804221721.51461.laurentp@cse-semaphore.com>
Date:	Tue, 22 Apr 2008 17:21:49 +0200
From:	Laurent Pinchart <laurentp@...-semaphore.com>
To:	Scott Wood <scottwood@...escale.com>
Cc:	linuxppc-dev@...abs.org, avorontsov@...mvista.com,
	netdev@...r.kernel.org
Subject: Re: [RFC fs_enet: Convert MII bitbang driver to use GPIO lib

On Tuesday 22 April 2008 17:08, Scott Wood wrote:
> On Tue, Apr 22, 2008 at 10:55:06AM +0200, Laurent Pinchart wrote:
> > On Monday 21 April 2008 19:56, Scott Wood wrote:
> > > The memory-constrained platform I had in mind was 8xx, which doesn't use
> > > bitbanged MDIO.  It might nice to keep the gpiolib bit separate to avoid
> > > situations such as ep8248e where mdiobb would be the only thing
> > > requiring a gpiolib binding, though -- but it shouldn't be two separate
> > > bitbang drivers, just the existing bitbang driver plus some glue code
> > > that binds it to gpiolib.
> > 
> > I would be fine with that if the glue code wasn't 90% of the whole driver. 
> > There is really little (not to say nothing) that can be shared between the 
> > two drivers.
> 
> I think we're thinking of a different pair of drivers...  I thought you
> were talking about duplicating drivers/net/phy/mdio-bitbang.c, not
> drivers/net/fs_enet/mii-bitbang.c.

I don't plan to touch drivers/net/phy/mdio-bitbang.c at all, it does its job 
well enough.

As the openfirmware + gpio + mdio driver might benefit non-powerpc platforms, 
I plan to create a new driver (probably drivers/net/phy/mdio-ofgpio.c) that 
mostly ports drivers/net/fs_enet/mii-bitbang.c to the gpiolib (this replaces 
around 90% of the code).

If both drivers/net/fs_enet/mii-bitbang.c and drivers/net/phy/mdio-ofgpio.c 
must live together, I'll have a problem in 
drivers/net/fs_enet/fs_enet-main.c. The net device probing code searches the 
device tree for an associated PHY, and creates a PHY id from the PHY node. As 
the id will be generated from different bus ids in the two mdio drivers (the 
bus number is the register address for drivers/net/fs_enet/mii-bitbang.c, and 
is the gpio index for drivers/net/phy/mdio-ofgpio.c), things will break.

Any idea regarding how to get rid of that fs_enet/mii-bitbang hardcoded 
dependency ?

-- 
Laurent Pinchart
CSE Semaphore Belgium

Chaussee de Bruxelles, 732A
B-1410 Waterloo
Belgium

T +32 (2) 387 42 59
F +32 (2) 387 42 75

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