linux-kernel - Re: [PATCH 4/7] gpiolib: implement dev_gpiochip

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Date:	Wed, 22 Oct 2008 13:27:14 +1100
From:	Benjamin Herrenschmidt <benh@...nel.crashing.org>
To:	avorontsov@...mvista.com
Cc:	David Brownell <david-b@...bell.net>,
	David Brownell <dbrownell@...rs.sourceforge.net>,
	linux-kernel@...r.kernel.org, linuxppc-dev@...abs.org,
	i2c@...sensors.org, Jean Delvare <khali@...ux-fr.org>,
	David Miller <davem@...emloft.net>
Subject: Re: [PATCH 4/7] gpiolib: implement dev_gpiochip_{add,remove} calls

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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