linux-kernel - Re: [RFC 2/4] driver core: Allow early registration of devices

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Date:	Fri, 16 Aug 2013 14:06:37 -0700
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	Thierry Reding <thierry.reding@...il.com>
Cc:	Grant Likely <grant.likely@...aro.org>,
	Rob Herring <rob.herring@...xeda.com>,
	Stephen Warren <swarren@...dotorg.org>,
	Hiroshi Doyu <hdoyu@...dia.com>,
	Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
	Sebastian Hesselbarth <sebastian.hesselbarth@...il.com>,
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [RFC 2/4] driver core: Allow early registration of devices

On Fri, Aug 16, 2013 at 10:39:21PM +0200, Thierry Reding wrote:
> +static DEFINE_MUTEX(device_early_mutex);
> +static LIST_HEAD(device_early_list);
> +static bool device_is_early = true;
> +
> +/*
> + * Keep a list of early registered devices so that they can be fully
> + * registered at a later point in time.
> + */
> +static void device_early_add(struct device *dev)

__init?

> +{
> +	mutex_lock(&device_early_mutex);
> +	list_add_tail(&dev->p->early, &device_early_list);
> +	mutex_unlock(&device_early_mutex);
> +}
> +
> +/*
> + * Mark the early device registration phase as completed.
> + */
> +int __init device_early_init(void)
> +{
> +	device_is_early = false;
> +
> +	return 0;
> +}
> +
> +/*
> + * Fixup platform devices instantiated from device tree. The problem is
> + * that since early registration happens before interrupt controllers
> + * have been setup, the OF core code won't know how to map interrupts.
> + */
> +int __init platform_device_early_fixup(struct platform_device *pdev)

This shouldn't be in this file, because:

> +/*
> + * Fully register early devices.
> + */
> +int __init device_early_done(void)
> +{
> +	struct device_private *private;
> +
> +	list_for_each_entry(private, &device_early_list, early) {
> +		struct device *dev = private->device;
> +		int err;
> +
> +		if (dev->bus == &platform_bus_type) {

Why special case the platform bus?  We are trying to move things off of
the platform bus, don't make it harder to do that :)

> +			struct platform_device *pdev = to_platform_device(dev);
> +
> +			err = platform_device_early_fixup(pdev);
> +			if (err < 0)
> +				dev_err(&pdev->dev,
> +					"failed to fixup device %s: %d\n",
> +					dev_name(&pdev->dev), err);
> +		}

You should just have a bus callback that can be made here that, if
present, can be called.  That way any bus can handle this type of thing,
not just the platform one.


Not that I really like the whole idea anyway, but I doubt there's much I
can do about it...

thanks,

greg k-h
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