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resources: Add lookup_resource()

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Add a function to find an existing resource by a resource start address.
This allows to implement simple allocators (with a malloc/free-alike API)
on top of the resource system.

Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
This commit is contained in:
Geert Uytterhoeven 2011-05-07 20:53:16 +02:00
commit 1c388919d8
2 changed files with 22 additions and 0 deletions
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1
include/linux/ioport.h
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@ -132,6 +132,7 @@ extern int allocate_resource(struct resource *root, struct resource *new,
resource_size_t, resource_size_t,
resource_size_t), resource_size_t),
void *alignf_data); void *alignf_data);
struct resource *lookup_resource(struct resource *root, resource_size_t start);
int adjust_resource(struct resource *res, resource_size_t start, int adjust_resource(struct resource *res, resource_size_t start,
resource_size_t size); resource_size_t size);
resource_size_t resource_alignment(struct resource *res); resource_size_t resource_alignment(struct resource *res);

21
kernel/resource.c
View file

@ -553,6 +553,27 @@ int allocate_resource(struct resource *root, struct resource *new,
EXPORT_SYMBOL(allocate_resource); EXPORT_SYMBOL(allocate_resource);
/**
* lookup_resource - find an existing resource by a resource start address
* @root: root resource descriptor
* @start: resource start address
*
* Returns a pointer to the resource if found, NULL otherwise
*/
struct resource *lookup_resource(struct resource *root, resource_size_t start)
{
struct resource *res;
read_lock(&resource_lock);
for (res = root->child; res; res = res->sibling) {
if (res->start == start)
break;
}
read_unlock(&resource_lock);
return res;
}
/* /*
* Insert a resource into the resource tree. If successful, return NULL, * Insert a resource into the resource tree. If successful, return NULL,
* otherwise return the conflicting resource (compare to __request_resource()) * otherwise return the conflicting resource (compare to __request_resource())