Re: [PATCH 4/7] gpiolib: implement dev_gpiochip_{add, remove} calls

From: Benjamin Herrenschmidt <benh-XVmvHMARGAS8U2dJNN8I7kB+6BGkLq7r@public.gmane.org>
To: avorontsov-hkdhdckH98+B+jHODAdFcQ@public.gmane.org
Cc: David Brownell
	<dbrownell-Rn4VEauK+AKRv+LV9MX5uipxlwaOVQ5f@public.gmane.org>,
	linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
	David Brownell <david-b-yBeKhBN/0LDR7s880joybQ@public.gmane.org>,
	linuxppc-dev-mnsaURCQ41sdnm+yROfE0A@public.gmane.org,
	i2c-GZX6beZjE8VD60Wz+7aTrA@public.gmane.org,
	David Miller <davem-fT/PcQaiUtIeIZ0/mPfg9Q@public.gmane.org>
Subject: Re: [PATCH 4/7] gpiolib: implement dev_gpiochip_{add, remove} calls
Date: Wed, 22 Oct 2008 13:27:14 +1100	[thread overview]
Message-ID: <1224642434.7654.317.camel@pasglop> (raw)
In-Reply-To: <20081022010347.GA7377-wnGakbxT3iijyJ0x5qLZdcN33GVbZNy3@public.gmane.org>

On Wed, 2008-10-22 at 05:03 +0400, Anton Vorontsov wrote:
> If say "X" driver loads prior to bus-notifier module (where we fill
> the platform data), then X.0 device will try to probe w/o platform
> data and will fail. The only way to re-probe things is to rmmod X &&
> insmod of_pdata_filler_X && insmod X. So things depend on the module
> load order.
> 
> The obvious solution is to link the OF stuff into the module, but
> this also won't work, since modules have only one entry (and exit)
> point. So there is no way* to hook our OF helpers into the module.

Well, right, we need the bus notifier to be registered before any
device gets added ... which mean from the same module_init that
registers the bus itself. A bit annoying ...

> * Well, there is one solution to this problem. We can implement
> arch-specific init_module and cleanup_module entry/exit points,
> where we can load/unload the OF hooks. This is quite easy, but
> may look ugly. I could show the drafts.

Yuck :-)

Cheers,
Ben.

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