linux-kernel - Re: [PATCH v3] mfd: syscon: Add non-DT support

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Message-Id: <201302181602.47157.arnd@arndb.de>
Date:	Mon, 18 Feb 2013 16:02:46 +0000
From:	Arnd Bergmann <arnd@...db.de>
To:	Alexander Shiyan <shc_work@...l.ru>
Cc:	linux-kernel@...r.kernel.org,
	Dong Aisheng <dong.aisheng@...aro.org>,
	Samuel Ortiz <sameo@...ux.intel.com>,
	Mark Brown <broonie@...nsource.wolfsonmicro.com>
Subject: Re: [PATCH v3] mfd: syscon: Add non-DT support

On Monday 18 February 2013, Alexander Shiyan wrote:
> diff --git a/drivers/mfd/syscon.c b/drivers/mfd/syscon.c
> index 4a7ed5a..3c0abcb 100644
> --- a/drivers/mfd/syscon.c
> +++ b/drivers/mfd/syscon.c

Hi Alexander,

>  struct regmap *syscon_regmap_lookup_by_compatible(const char *s)
>  {
>  	struct device_node *syscon_np;
>  	struct regmap *regmap;
> +	struct syscon *syscon;
> +	struct device *dev;
>  
>  	syscon_np = of_find_compatible_node(NULL, NULL, s);
> -	if (!syscon_np)
> +	if (syscon_np) {
> +		regmap = syscon_node_to_regmap(syscon_np);
> +		of_node_put(syscon_np);
> +
> +		return regmap;
> +	}
> +
> +	/* Fallback to search by id_entry.name string */
> +	dev = driver_find_device(&syscon_driver.driver, NULL, (void *)s,
> +				 syscon_match_id);
> +	if (!dev)
>  		return ERR_PTR(-ENODEV);
>  
> -	regmap = syscon_node_to_regmap(syscon_np);
> -	of_node_put(syscon_np);
> +	syscon = dev_get_drvdata(dev);
>  
> -	return regmap;
> +	return syscon->regmap;
>  }
>  EXPORT_SYMBOL_GPL(syscon_regmap_lookup_by_compatible);

Since you are not actually comparing the "compatible" property here,
I would suggest adding another function here, something like
syscon_regmap_lookup_by_pdevname() that you can use in device
drivers that are not DT-enabled. I would also recommend enclosing
that function in #ifdef CONFIG_ATAGS.

Which code do you have in mind that would call this anyway?
The changeset description does not really explain what ATAG
boot support in syscon is good for.

> +	if (IS_ENABLED(CONFIG_OF) && np) {
> +		syscon->base = of_iomap(np, 0);
> +		if (!syscon->base)
> +			return -EADDRNOTAVAIL;
> +
> +		res = &res_of;
> +		ret = of_address_to_resource(np, 0, res);
> +		if (ret) {
> +			iounmap(syscon->base);
> +			return ret;
> +		}
> +	} else {
> +		res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> +		if (!res)
> +			return -ENOENT;
> +
> +		if (!devm_request_mem_region(dev, res->start,
> +					     resource_size(res),
> +					     dev_name(&pdev->dev)))
> +			return -EBUSY;
> +
> +		syscon->base = ioremap(res->start, resource_size(res));
> +		if (!syscon->base)
> +			return -EADDRNOTAVAIL;
> +	}

These two code paths look equivalent. Why not always use the second
one? Also, you might want to convert this to devm_ioremap_resource()
to simplify the code in the process.

	Arnd
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