linux-kernel - Re: [PATCH v2-UPDATE 3/4] resource: Add device-managed insert/remove

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Date:	Tue, 8 Mar 2016 13:02:53 +0100
From:	Ingo Molnar <mingo@...nel.org>
To:	Toshi Kani <toshi.kani@....com>
Cc:	bp@...e.de, dan.j.williams@...el.com, rjw@...ysocki.net,
	akpm@...ux-foundation.org, linux-nvdimm@...ts.01.org,
	linux-acpi@...r.kernel.org, linux-kernel@...r.kernel.org,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH v2-UPDATE 3/4] resource: Add device-managed
 insert/remove_resource()


* Toshi Kani <toshi.kani@....com> wrote:

> +/**
> + * devm_insert_resource() - insert an I/O or memory resource
> + * @dev: device for which to produce the resource
> + * @root: root of the resource tree
> + * @new: descriptor of the new resource
> + *
> + * This is a device-managed version of insert_resource(). There is usually
> + * no need to release resources requested by this function explicitly since

s/explicitly since
 /explicitly, since

> + * that will be taken care of when the device is unbound from its bus driver.
> + * If for some reason the resource needs to be released explicitly, because
> + * of ordering issues for example, bus drivers must call devm_remove_resource()
> + * rather than the regular remove_resource().
> + *
> + * devm_insert_resource() is intended for producers of resources, such as
> + * FW modules and bus drivers.
> + *
> + * Returns 0 on success or a negative error code on failure.
> + */
> +int devm_insert_resource(struct device *dev, struct resource *root,
> +			  struct resource *new)
> +{
> +	struct resource **ptr;
> +	int ret;
> +
> +	ptr = devres_alloc(__devm_remove_resource, sizeof(*ptr), GFP_KERNEL);
> +	if (!ptr)
> +		return -ENOMEM;
> +
> +	*ptr = new;
> +
> +	ret = insert_resource(root, new);
> +	if (ret) {
> +		dev_err(dev, "unable to insert resource: %pR (%d)\n", new, ret);
> +		devres_free(ptr);
> +		return -EBUSY;

Why not return 'ret' here, instead of -EBUSY?

> +	}
> +
> +	devres_add(dev, ptr);
> +	return 0;
> +}
> +EXPORT_SYMBOL_GPL(devm_insert_resource);
> +
> +/**
> + * devm_remove_resource() - remove a previously inserted resource
> + * @dev: device for which to remove the resource
> + * @old: descriptor of the resource
> + *
> + * Remove a resource previously inserted using devm_insert_resource().
> + *
> + * devm_remove_resource() is intended for producers of resources, such as
> + * FW modules and bus drivers.
> + */
> +void devm_remove_resource(struct device *dev, struct resource *old)
> +{
> +	WARN_ON(devres_release(dev, __devm_remove_resource, devm_resource_match,
> +			       old));

So generally we don't put functions with side effects into WARN_ON()s. Just like 
BUG_ON(), in the future it might be disabled on certain Kconfigs, etc. - and it's 
also bad for readability.

Also, please use WARN_ON_ONCE().

> +}
> +EXPORT_SYMBOL_GPL(devm_remove_resource);
> +
> +/*
>   * Called from init/main.c to reserve IO ports.
>   */
>  #define MAXRESERVE 4

Looks good to me otherwise.

Thanks,

	Ingo