request_resource

1.全局变量

resource结构体定义如下，指针parent、sibling、child用于构建树状结构。

struct resource {
    resource_size_t start;
    resource_size_t end;
    const char *name;
    unsigned long flags;
    struct resource *parent, *sibling, *child;
};

用到的全局变量

/arch/arm/kernel/setup.c/
static struct resource mem_res[] = {
    {
        .name = "Video RAM",
        .start = 0,
        .end = 0,
        .flags = IORESOURCE_MEM
    },
    {
        .name = "Kernel text",
        .start = 0,
        .end = 0,
        .flags = IORESOURCE_MEM
    },
    {
        .name = "Kernel data",
        .start = 0,
        .end = 0,
        .flags = IORESOURCE_MEM
    }
};

#define video_ram   mem_res[0]
#define kernel_code mem_res[1]
#define kernel_data mem_res[2]

2.request_resource()

int request_resource(struct resource *root, struct resource *new)
    -->__request_resource(root, new);//按地址升序排列

/* Return the conflict entry if you can't request it */
static struct resource * __request_resource(struct resource *root, struct resource *new)
{
    resource_size_t start = new->start;
    resource_size_t end = new->end;
    struct resource *tmp, **p;

    if (end < start)
        return root;
    if (start < root->start)
        return root;
    if (end > root->end)
        return root;
    p = &root->child;
    for (;;) {
        tmp = *p;
        if (!tmp || tmp->start > end) {
            new->sibling = tmp;
            *p = new;
            new->parent = root;
            return NULL;
        }
        p = &tmp->sibling;
        if (tmp->end < start)
            continue;
        return tmp;
    }
}