linux-kernel - Re: [PATCH (Option 1)] of/i2c: fix module load order issue caused by of

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Message-ID: <20100928232147.GR21564@trinity.fluff.org>
Date:	Wed, 29 Sep 2010 00:21:47 +0100
From:	Ben Dooks <ben-i2c@...ff.org>
To:	Grant Likely <grant.likely@...retlab.ca>
Cc:	khali@...ux-fr.org, mikpe@...uu.se, rdunlap@...otime.net,
	linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org,
	linux-i2c@...r.kernel.org
Subject: Re: [PATCH (Option 1)] of/i2c: fix module load order issue caused
	by of_i2c.c

On Fri, Sep 24, 2010 at 04:14:53PM -0600, Grant Likely wrote:
> Commit 959e85f7, "i2c: add OF-style registration and binding" caused a
> module dependency loop where of_i2c.c calls functions in i2c-core, and
> i2c-core calls of_i2c_register_devices() in of_i2c.  This means that
> when i2c support is built as a module when CONFIG_OF is set, then
> neither i2c_core nor of_i2c are able to be loaded.
> 
> This patch fixes the problem by moving the of_i2c_register_devices()
> function into the body of i2c_core and renaming it to
> i2c_scan_of_devices (of_i2c_register_devices is analogous to the
> existing i2c_scan_static_board_info function and so should be named
> similarly).  This function isn't called by any code outside of
> i2c_core, and it must always be present when CONFIG_OF is selected, so
> it makes sense to locate it there.  When CONFIG_OF is not selected,
> of_i2c_register_devices() becomes a no-op.
> 
> Signed-off-by: Grant Likely <grant.likely@...retlab.ca>
> ---
>  drivers/i2c/i2c-core.c |   61 ++++++++++++++++++++++++++++++++++++++++++++++--
>  drivers/of/of_i2c.c    |   57 ---------------------------------------------
>  include/linux/of_i2c.h |    7 ------
>  3 files changed, 59 insertions(+), 66 deletions(-)
> 
> diff --git a/drivers/i2c/i2c-core.c b/drivers/i2c/i2c-core.c
> index 6649176..64a261b 100644
> --- a/drivers/i2c/i2c-core.c
> +++ b/drivers/i2c/i2c-core.c
> @@ -32,8 +32,8 @@
>  #include <linux/init.h>
>  #include <linux/idr.h>
>  #include <linux/mutex.h>
> -#include <linux/of_i2c.h>
>  #include <linux/of_device.h>
> +#include <linux/of_irq.h>
>  #include <linux/completion.h>
>  #include <linux/hardirq.h>
>  #include <linux/irqflags.h>
> @@ -818,6 +818,63 @@ static void i2c_scan_static_board_info(struct i2c_adapter *adapter)
>  	up_read(&__i2c_board_lock);
>  }
>  
> +#ifdef CONFIG_OF
> +void i2c_scan_of_devices(struct i2c_adapter *adap)
> +{
> +	void *result;
> +	struct device_node *node;
> +
> +	/* Only register child devices if the adapter has a node pointer set */
> +	if (!adap->dev.of_node)
> +		return;
> +
> +	for_each_child_of_node(adap->dev.of_node, node) {
> +		struct i2c_board_info info = {};
> +		struct dev_archdata dev_ad = {};
> +		const __be32 *addr;
> +		int len;
> +
> +		dev_dbg(&adap->dev, "of_i2c: register %s\n", node->full_name);
> +		if (of_modalias_node(node, info.type, sizeof(info.type)) < 0) {
> +			dev_err(&adap->dev, "of_i2c: modalias failure on %s\n",
> +				node->full_name);
> +			continue;
> +		}
> +
> +		addr = of_get_property(node, "reg", &len);
> +		if (!addr || (len < sizeof(int))) {
> +			dev_err(&adap->dev, "of_i2c: invalid reg on %s\n",
> +				node->full_name);
> +			continue;
> +		}
> +
> +		info.addr = be32_to_cpup(addr);
> +		if (info.addr > (1 << 10) - 1) {
> +			dev_err(&adap->dev, "of_i2c: invalid addr=%x on %s\n",
> +				info.addr, node->full_name);
> +			continue;
> +		}
> +
> +		info.irq = irq_of_parse_and_map(node, 0);
> +		info.of_node = of_node_get(node);
> +		info.archdata = &dev_ad;
> +
> +		request_module("%s", info.type);
> +
> +		result = i2c_new_device(adap, &info);
> +		if (result == NULL) {
> +			dev_err(&adap->dev, "of_i2c: Failure registering %s\n",
> +			        node->full_name);
> +			of_node_put(node);
> +			irq_dispose_mapping(info.irq);
> +			continue;
> +		}
> +	}
> +}
> +#else
> +static inline void i2c_scan_of_devices(struct i2c_adapter *adap) { }
> +#endif

Is there any advantage to just making the definition in the header
file a static inline and removing the #else part of this?

-- 
Ben

Q:      What's a light-year?
A:      One-third less calories than a regular year.

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