On Mon, Oct 03, 2005 at 03:43:50PM +0300, Pekka Enberg wrote:
> Usually yes but it makes releasing partial initialization much simpler
> because you can reuse the normal release counterpart. For example,
>
> static int driver_init(void)
> {
> dev->resource1 = request_region(...);
> if (!dev->resource1)
> goto failed;
>
> dev->resource2 = request_region(...);
> if (!dev->resource2)
> goto failed;
>
> return 0;
>
> failed:
> driver_release(dev);
> return -1;
> }
>
> static void driver_release(struct device * dev)
> {
> release_resource(dev->resource1);
> release_resource(dev->resource2);
> kfree(dev);
> }
>
> Many drivers have the release function copy-pasted to init with lots
> of goto labels exactly because release_region, iounmap, and friends
> aren't NULL safe.
And the above is buggy. request_region() allocates memory.
release_resource() unregisters the resource but does _not_
free the allocated memory.
On the other hand, release_region() is the counter-part of
request_region() and should be used to release resources
created by request_region().
--
Russell King
Linux kernel 2.6 ARM Linux - http://www.arm.linux.org.uk/
maintainer of: 2.6 Serial core
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