devres驱动笔记

参考：

devres in linux driver - sammei - 博客园

1、devres_alloc函数：

源码路径：include/linux/device.h 

static inline void *devres_alloc(dr_release_t release, size_t size, gfp_t gfp)
{
        return devres_alloc_node(release, size, gfp, NUMA_NO_NODE);
}

devres_alloc_node函数源码路径：drivers/base/devres.c

void * devres_alloc_node(dr_release_t release, size_t size, gfp_t gfp, int nid)
{
	struct devres *dr;
 
	dr = alloc_dr(release, size, gfp | __GFP_ZERO, nid);
 
	return dr->data;
}

static __always_inline struct devres * alloc_dr(dr_release_t release,
						size_t size, gfp_t gfp, int nid)
{
	size_t tot_size = sizeof(struct devres) + size;
	struct devres *dr;
 
	memset(dr, 0, offsetof(struct devres, data)); //将data成员前面的内存都清零
 
	INIT_LIST_HEAD(&dr->node.entry);
	dr->node.release = release;
	return dr;
}

2、struct devres结构体定义：

struct devres {
	struct devres_node		node;
 
	u8 __aligned(ARCH_KMALLOC_MINALIGN) data[];
};

3、举例：

struct regmap *__devm_regmap_init(struct device *dev,...)
{
	struct regmap **ptr, *regmap;
    
    //data指向分配的资源*ptr,所以指针的指针是二维指针
	ptr = devres_alloc(devm_regmap_release, sizeof(*ptr), GFP_KERNEL);
    ......
}

4、devres_add函数：

 

void devres_add(struct device *dev, void *res)
{
	struct devres *dr = container_of(res, struct devres, data);
    ......
	add_dr(dev, &dr->node);
}

static void add_dr(struct device *dev, struct devres_node *node)
{
	list_add_tail(&node->entry, &dev->devres_head);
}

5、其它API函数：