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

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Date:	Tue, 08 Mar 2016 10:41:47 -0700
From:	Toshi Kani <toshi.kani@....com>
To:	Ingo Molnar <mingo@...nel.org>
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()

On Tue, 2016-03-08 at 13:02 +0100, Ingo Molnar wrote:
> * 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

Will do.

> > + * 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?

Right, I will change it to 'return ret'.

> > +	}
> > +
> > +	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().

I see.  Will change to test with WARN_ON_ONCE(ret).

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

Great!  I will send an updated patch as "[PATCH v2-UPDATE2 3/4]".

Thanks,
-Toshi