linux-kernel - Re: [PATCH 0/3] capebus moving omap

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Message-Id: <C9715CB7-D3E2-4CA7-8A93-2B10E8B70640@antoniou-consulting.com>
Date:	Wed, 31 Oct 2012 20:04:05 +0200
From:	Pantelis Antoniou <panto@...oniou-consulting.com>
To:	Tony Lindgren <tony@...mide.com>
Cc:	linux-kernel@...r.kernel.org,
	Koen Kooi <koen@...inion.thruhere.net>,
	Matt Porter <mporter@...com>, Russ Dill <Russ.Dill@...com>,
	linux-omap@...r.kernel.org
Subject: Re: [PATCH 0/3] capebus moving omap_devices to mach-omap2

Hi Tony,

On Oct 31, 2012, at 7:52 PM, Tony Lindgren wrote:

> * Pantelis Antoniou <panto@...oniou-consulting.com> [121031 10:26]:
>> It is painless to move the adapter DT devices to arch/arm/mach-omap2
>> 
>> However I got bit by the __init at omap_build_device family functions.
>> If you don't remove it, crashes every time you instantiate a device
>> at runtime, or you load the cape driver as a module.
> 
> Hmm I think you misunderstood me. You only need to create the
> platform_device under arch/arm/mach-omap2. The device creation
> happens only at __init, so omap_build_device can stay as __init.
> The driver itself should be under drivers.
> 
> But is this bus on non-device-tree omaps? If not, just make it
> device tree only.
> 

I'm afraid that's not the case. The whole notion of capebus is that
instantiation of the devices doesn't just happen early at the boot
sequence.

It is perfectly valid for a cape to be instantiated via loading
a module, or by making an override by writing a sysfs file.

When having the __init there, the function has been long removed
and you get a crash by calling into the weeds.

So the sequence is:

<early boot>       Register the adapter driver.

<user>             insmod bone-geiger-cape
<cape-is-matched>  call omap_build_device

Please look into the capebus patches for the details. 

> Regards,
> 
> Tony

Regards

-- Pantelis

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