Re: [PATCH] PNP: Switch from __check_region() to __request_region()

[Jakub Sitnicki <jsitnicki@gmail.com>]

Rafael J. Wysocki <rjw@rjwysocki.net> writes:

> On Monday, December 08, 2014 10:01:57 PM Jakub Sitnicki wrote:
>> diff --git a/drivers/pnp/resource.c b/drivers/pnp/resource.c
>> index 782e822..f980ff7 100644
>> --- a/drivers/pnp/resource.c
>> +++ b/drivers/pnp/resource.c
>> @@ -179,8 +179,9 @@ int pnp_check_port(struct pnp_dev *dev, struct resource *res)
>>  	/* check if the resource is already in use, skip if the
>>  	 * device is active because it itself may be in use */
>>  	if (!dev->active) {
>> -		if (__check_region(&ioport_resource, *port, length(port, end)))
>> +		if (!request_region(*port, length(port, end), "pnp"))
>>  			return 0;
>> +		release_region(*port, length(port, end));
>
> Shouldn't we also release the resource returned by request_region() if it is
> not NULL?
>

Thanks for taking a look at this. I think we're good here. If you please
bear with me for a moment:

release_resource() removes an element from the list of resource parent's
children (and makes it an orphan):

	p = &old->parent->child;
	for (;;) {
		tmp = *p;
		if (!tmp)
			break;
		if (tmp == old) {
			*p = tmp->sibling;
			old->parent = NULL;
			return 0;
		}
		p = &tmp->sibling;
	}

release_region() does the same but with additional checks, and also
frees the resource:

	p = &parent->child;
        /* ... */
	for (;;) {
		struct resource *res = *p;

		if (!res)
			break;
		if (res->start <= start && res->end >= end) {
                        /* ... */
			*p = res->sibling;
                        /* ... */
			free_resource(res);
			return;
		}
		p = &res->sibling;
	}

When making the change I've based on other code in the kernel which also
make use of request_region().

To quote one example, drivers/net/ethernet/8390/ne2k-pci.c cleans up its
I/O port region when initialization fails like so:

static int ne2k_pci_init_one(struct pci_dev *pdev,
			     const struct pci_device_id *ent)
{
        /* ... */

	if (request_region (ioaddr, NE_IO_EXTENT, DRV_NAME) == NULL) {
		dev_err(&pdev->dev, "I/O resource 0x%x @ 0x%lx busy\n",
			NE_IO_EXTENT, ioaddr);
		return -EBUSY;
	}

        /* ... */

	dev = alloc_ei_netdev();
	if (!dev) {
		dev_err(&pdev->dev, "cannot allocate ethernet device\n");
		goto err_out_free_res;
	}

        /* ... */

err_out_free_res:
	release_region (ioaddr, NE_IO_EXTENT);
	return -ENODEV;
}

>>  	}
>>  
>>  	/* check if the resource is reserved */
>> @@ -241,8 +242,9 @@ int pnp_check_mem(struct pnp_dev *dev, struct resource *res)
>>  	/* check if the resource is already in use, skip if the
>>  	 * device is active because it itself may be in use */
>>  	if (!dev->active) {
>> -		if (check_mem_region(*addr, length(addr, end)))
>> +		if (!request_mem_region(*addr, length(addr, end), "pnp"))
>>  			return 0;
>> +		release_mem_region(*addr, length(addr, end));
>>  	}
>>  
>>  	/* check if the resource is reserved */
>>