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SubjectRe: [PATCH] PNP: Switch from __check_region() to __request_region()
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On Fri, Dec 12, 2014 at 08:47 AM CET, Jakub Sitnicki wrote:
> 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;
> }

Just wondering, do you have any further thoughts on this?

Thanks,
Jakub


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