了解linux-5.4.31/drivers/gpio/gpiolib-devres.c中的devm_gpiod_get_optional()函数
1、打开“drivers/gpio/gpiolib-devres.c”
/**
获取GPIO线的索引,查找“设备资源”,分配“设备资源数据”,注册“设备资源”;
* devm_gpiod_get_optional - Resource-managed gpiod_get_optional()
* @dev: GPIO consumer
* @con_id: function within the GPIO consumer
* @flags: optional GPIO initialization flags
*
* Managed gpiod_get_optional(). GPIO descriptors returned from this function
* are automatically disposed on driver detach. See gpiod_get_optional() for
* detailed information about behavior and return values.
*/
//sii902x->reset_gpio = devm_gpiod_get_optional(dev, "reset",GPIOD_OUT_LOW);
struct gpio_desc *__must_check devm_gpiod_get_optional(struct device *dev,
const char *con_id,
enum gpiod_flags flags)
{
return devm_gpiod_get_index_optional(dev, con_id, 0, flags);
}
/**
获取GPIO线的索引,查找“设备资源”,分配“设备资源数据”,注册“设备资源”;
* devm_gpiod_get_index_optional - Resource-managed gpiod_get_index_optional()
* @dev: GPIO consumer
* @con_id: function within the GPIO consumer
* @index: index of the GPIO to obtain in the consumer
* @flags: optional GPIO initialization flags
*
* Managed gpiod_get_index_optional(). GPIO descriptors returned from this
* function are automatically disposed on driver detach. See
* gpiod_get_index_optional() for detailed information about behavior and
* return values.
*/
struct gpio_desc *__must_check devm_gpiod_get_index_optional(struct device *dev,
const char *con_id,
unsigned int index,
enum gpiod_flags flags)
{
struct gpio_desc *desc;
desc = devm_gpiod_get_index(dev, con_id, index, flags);
//获取GPIO线的索引,查找“设备资源”,分配“设备资源数据”,注册“设备资源”;
if (IS_ERR(desc)) {
if (PTR_ERR(desc) == -ENOENT)
return NULL;
}
return desc;
}
/**
获取GPIO线的索引,查找“设备资源”,分配“设备资源数据”,注册“设备资源”;
* devm_gpiod_get_index - Resource-managed gpiod_get_index()
* @dev: GPIO consumer
* @con_id: function within the GPIO consumer
* @idx: index of the GPIO to obtain in the consumer
* @flags: optional GPIO initialization flags
*
* Managed gpiod_get_index(). GPIO descriptors returned from this function are
* automatically disposed on driver detach. See gpiod_get_index() for detailed
* information about behavior and return values.
*/
struct gpio_desc *__must_check devm_gpiod_get_index(struct device *dev,
const char *con_id,
unsigned int idx,
enum gpiod_flags flags)
{
struct gpio_desc **dr;
struct gpio_desc *desc;
desc = gpiod_get_index(dev, con_id, idx, flags);//用于获取GPIO线的索引
if (IS_ERR(desc))
return desc;
/*
* For non-exclusive GPIO descriptors, check if this descriptor is
* already under resource management by this device.
*/
if (flags & GPIOD_FLAGS_BIT_NONEXCLUSIVE) {
struct devres *dres;
dres = devres_find(dev, devm_gpiod_release,devm_gpiod_match, &desc);
//查找设备资源
if (dres) return desc;
}
dr = devres_alloc(devm_gpiod_release, sizeof(struct gpio_desc *),GFP_KERNEL);
//分配设备资源数据
if (!dr) {
gpiod_put(desc);
//释放一个已经申请的GPIO资源，释放后该GPIO可以被其他设备或应用程序使用;
return ERR_PTR(-ENOMEM);
}
*dr = desc;
devres_add(dev, dr);//注册设备资源
return desc;
}
/**
* devres_find - 查找设备资源Find device resource
* @dev: Device to lookup resource from
* @release: Look for resources associated with this release function
* @match: Match function (optional)
* @match_data: Data for the match function
*
* Find the latest devres of @dev which is associated with @release
* and for which @match returns 1. If @match is NULL, it's considered
* to match all.
*
* RETURNS:
* Pointer to found devres, NULL if not found.
*/
void * devres_find(struct device *dev, dr_release_t release,
dr_match_t match, void *match_data)
{
struct devres *dr;
unsigned long flags;
spin_lock_irqsave(&dev->devres_lock, flags);
dr = find_dr(dev, release, match, match_data);
spin_unlock_irqrestore(&dev->devres_lock, flags);
if (dr)
return dr->data;
return NULL;
}
2、打开“drivers/gpio/gpiolib.c”
/**
* gpiod_put - 处理一个GPIO描述符,dispose of a GPIO descriptor
* @desc: GPIO descriptor to dispose of
*
* No descriptor can be used after gpiod_put() has been called on it.
*/
void gpiod_put(struct gpio_desc *desc)
{
if (desc)
gpiod_free(desc);
//用于释放一个已经申请的GPIO资源，释放后该GPIO可以被其他设备或应用程序使用;
}
3、打开“include/linux/device.h”
#define devres_alloc(release, size, gfp) \
__devres_alloc_node(release, size, gfp, NUMA_NO_NODE, #release)
4、打开“drivers/base/devres.c”
/**
* devres_alloc - 分配设备资源数据，Allocate device resource data
* @release: Release function devres will be associated with
* @size: Allocation size
* @gfp: Allocation flags
* @nid: NUMA node
*
* Allocate devres of @size bytes. The allocated area is zeroed, then
* associated with @release. The returned pointer can be passed to
* other devres_*() functions.
*
* RETURNS:
* Pointer to allocated devres on success, NULL on failure.
*/
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);
if (unlikely(!dr))
return NULL;
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;
struct devres *dr;
/* We must catch any near-SIZE_MAX cases that could overflow. */
if (unlikely(check_add_overflow(sizeof(struct devres), size,
&tot_size)))
return NULL;
dr = kmalloc_node_track_caller(tot_size, gfp, nid);
if (unlikely(!dr))
return NULL;
memset(dr, 0, offsetof(struct devres, data));
INIT_LIST_HEAD(&dr->node.entry);
dr->node.release = release;
return dr;
}
/**
* devres_add - 注册设备资源,Register device resource
* @dev: Device to add resource to
* @res: Resource to register
*
* Register devres @res to @dev. @res should have been allocated
* using devres_alloc(). On driver detach, the associated release
* function will be invoked and devres will be freed automatically.
*/
void devres_add(struct device *dev, void *res)
{
struct devres *dr = container_of(res, struct devres, data);
unsigned long flags;
spin_lock_irqsave(&dev->devres_lock, flags);
add_dr(dev, &dr->node);
spin_unlock_irqrestore(&dev->devres_lock, flags);
}