Platform 设备驱动：platform_get_drvdata 与 platform_set

Linux version: 4.14

Code link: Linux source code (v4.14) - Bootlin

1 函数原型

（1） platform_get_drvdata [ include/linux/platform_device.h: 211 ]

static inline void *platform_get_drvdata(const struct platform_device *pdev)
{return dev_get_drvdata(&pdev->dev);
}

其中 dev_get_drvdata [ include/linux/device.h: 1024 ]

static inline void *dev_get_drvdata(const struct device *dev)
{return dev->driver_data;
}

（2）platform_set_drvdata [ include/linux/platform_device.h: 216 ]

static inline void platform_set_drvdata(struct platform_device *pdev,void *data)
{dev_set_drvdata(&pdev->dev, data);
}

其中 dev_set_drvdata [ include/linux/device.h: 1029 ]

static inline void dev_set_drvdata(struct device *dev, void *data)
{dev->driver_data = data;
}

2 涉及的变量类型

（1）platform_device [ include/linux/platform_device.h: 23 ]

platform_device 是 platform设备结构体，主要关注里面 struct device dev;

struct platform_device {const char   *name;int       id;bool     id_auto;struct device   dev;u32     num_resources;struct resource   *resource;const struct platform_device_id   *id_entry;char *driver_override; /* Driver name to force a match *//* MFD cell pointer */struct mfd_cell *mfd_cell;/* arch specific additions */struct pdev_archdata    archdata;
};

（2）device [ include/linux/device.h: 888 ]

device 是一个通用的设备结构体，里面放的是每个设备都会有的通用数据。我们主要关注 void *platform_data; 这个变量。

struct device {struct device     *parent;struct device_private   *p;struct kobject kobj;const char       *init_name; /* initial name of the device */const struct device_type *type;struct mutex     mutex;  /* mutex to synchronize calls to* its driver.*/struct bus_type  *bus;       /* type of bus device is on */struct device_driver *driver; /* which driver has allocated thisdevice */void     *platform_data; /* Platform specific data, devicecore doesn't touch it */void      *driver_data;   /* Driver data, set and get withdev_set/get_drvdata */struct dev_links_info links;struct dev_pm_info    power;struct dev_pm_domain  *pm_domain;#ifdef CONFIG_GENERIC_MSI_IRQ_DOMAINstruct irq_domain    *msi_domain;
#endif
#ifdef CONFIG_PINCTRLstruct dev_pin_info    *pins;
#endif
#ifdef CONFIG_GENERIC_MSI_IRQstruct list_head   msi_list;
#endif#ifdef CONFIG_NUMAint     numa_node;  /* NUMA node this device is close to */
#endifconst struct dma_map_ops *dma_ops;u64     *dma_mask;  /* dma mask (if dma'able device) */u64     coherent_dma_mask;/* Like dma_mask, but foralloc_coherent mappings asnot all hardware supports64 bit addresses for consistentallocations such descriptors. */unsigned long  dma_pfn_offset;struct device_dma_parameters *dma_parms;struct list_head dma_pools;  /* dma pools (if dma'ble) */struct dma_coherent_mem    *dma_mem; /* internal for coherent memoverride */
#ifdef CONFIG_DMA_CMAstruct cma *cma_area;      /* contiguous memory area for dmaallocations */
#endif/* arch specific additions */struct dev_archdata  archdata;struct device_node *of_node; /* associated device tree node */struct fwnode_handle *fwnode; /* firmware device node */dev_t            devt;   /* dev_t, creates the sysfs "dev" */u32           id; /* device instance */spinlock_t     devres_lock;struct list_head    devres_head;struct klist_node   knode_class;struct class        *class;const struct attribute_group **groups;   /* optional groups */void   (*release)(struct device *dev);struct iommu_group   *iommu_group;struct iommu_fwspec    *iommu_fwspec;bool          offline_disabled:1;bool         offline:1;bool          of_node_reused:1;
};

（3）void *platform_data

platform_data 用来存放平台相关的初始化数据。使用 void * 可以让数据类型存在多种可能，即满足不同设备驱动的数据都能通过指针传参。其实这里是用来存放 platform_device 数据结构的，通过 platform_driver 和 platform_device 的名字进行匹配后，platform_driver 部分就可以使用platform_device 传过来的数据了。

小结：platform_get_drvdata 即为通过传入 struct platform_device 结构体类型的指针，得到设备传给驱动的数据。而 platform_set_drvdata 则将 platform_data 指向传入的数据。

3 应用例程

例如，对于DM9000网卡，为platform_data定义一个dm9000_plat_data结构体，定义完后，可以将MAC地址、总线宽度、板上有无EEPROM信息等放入platform_data中。

static struct dm9000_plat_data dm9000_platdata = {.flags = DM9000_PLATF_16BITONLY | DM9000_PLATF_NO_EEPROM,
};static struct platform_device dm9000_device = {.name = "dm9000",.id = 0,.num_resources = ARRAY_SIZE(dm9000_resource),.resource = dm9000_resource,.dev = {.platform_data = &dm9000_platdata, // 自定义设备数据}
};

在DM9000网卡驱动的probe()中，可这样拿到platform_data：

struct dm9000_plat_data *pdata = platform_get_drvdata(pdev);

4 参考

深度讲解Linux设备驱动的软件架构 - 知乎 (zhihu.com)