iTOP4412设备驱动学习二

Posted 2021-03-06 nanzh

以module的方式注册设备，并在驱动中调用设备的参数

资料来源于迅为视频学习。

前面一节的设备注册使用的是CONFIG_HELLO_CTL的形式，通过结构体platform_device的调用直接配置，实现注册设备的功能。

本节通过直接调用的注册设备的函数来是其功能。

主要函数：

platform_device_register  :drivers/base/platform.c

 1 流程：
 2 文件drivers/base/platform.c定义了设备的register函数，然后通过platform_device_add.
 3 所以我们只需要会使用platform_device_register即可。
 4 /**
 5  * platform_device_register - add a platform-level device
 6  * @pdev: platform device we‘re adding
 7  */
 8 int platform_device_register(struct platform_device *pdev)
 9 {
10         device_initialize(&pdev->dev);
11         return platform_device_add(pdev);
12 }
13 EXPORT_SYMBOL_GPL(platform_device_register);

platform_device_unregister：同上

 1 更详细的以后参考内核代码分析：
 2 /**
 3  * platform_device_unregister - unregister a platform-level device
 4  * @pdev: platform device we‘re unregistering
 5  *
 6  * Unregistration is done in 2 steps. First we release all resources
 7  * and remove it from the subsystem, then we drop reference count by
 8  * calling platform_device_put().
 9  */
10 void platform_device_unregister(struct platform_device *pdev)
11 {
12         platform_device_del(pdev);
13         platform_device_put(pdev);
14 }
15 EXPORT_SYMBOL_GPL(platform_device_unregister);

还有一个结构体：platform_device，作为上面两个函数的使用参数，结构体类型具体如下：

  1 /**
  2  * struct device - The basic device structure
  3  * @parent:     The device‘s "parent" device, the device to which it is attached.
  4  *              In most cases, a parent device is some sort of bus or host
  5  *              controller. If parent is NULL, the device, is a top-level device,
  6  *              which is not usually what you want.
  7  * @p:          Holds the private data of the driver core portions of the device.
  8  *              See the comment of the struct device_private for detail.
  9  * @kobj:       A top-level, abstract class from which other classes are derived.
 10  * @init_name:  Initial name of the device.
 11  * @type:       The type of device.
 12  *              This identifies the device type and carries type-specific
 13  *              information.
 14  * @mutex:      Mutex to synchronize calls to its driver.
 15  * @bus:        Type of bus device is on.
 16  * @driver:     Which driver has allocated this
 17  * @platform_data: Platform data specific to the device.
 18  *              Example: For devices on custom boards, as typical of embedded
 19  *              and SOC based hardware, Linux often uses platform_data to point
 20  *              to board-specific structures describing devices and how they
 21  *              are wired.  That can include what ports are available, chip
 22  *              variants, which GPIO pins act in what additional roles, and so
 23  *              on.  This shrinks the "Board Support Packages" (BSPs) and
 24  *              minimizes board-specific #ifdefs in drivers.
 25  * @power:      For device power management.
 26  *              See Documentation/power/devices.txt for details.
 27  * @pwr_domain: Provide callbacks that are executed during system suspend,
 28  *              hibernation, system resume and during runtime PM transitions
 29  *              along with subsystem-level and driver-level callbacks.
 30  * @numa_node:  NUMA node this device is close to.
 31  * @dma_mask:   Dma mask (if dma‘ble device).
 32  * @coherent_dma_mask: Like dma_mask, but for alloc_coherent mapping as not all
 33  *              hardware supports 64-bit addresses for consistent allocations
 34  *              such descriptors.
 35  * @dma_parms:  A low level driver may set these to teach IOMMU code about
 36  *              segment limitations.
 37  * @dma_pools:  Dma pools (if dma‘ble device).
 38  * @dma_mem:    Internal for coherent mem override.
 39  * @archdata:   For arch-specific additions.
 40  * @of_node:    Associated device tree node.
 41  * @devt:       For creating the sysfs "dev".
 42  * @devres_lock: Spinlock to protect the resource of the device.
 43  * @devres_head: The resources list of the device.
 44  * @knode_class: The node used to add the device to the class list.
 45  * @class:      The class of the device.
 46  * @groups:     Optional attribute groups.
 47  * @release:    Callback to free the device after all references have
 48  *              gone away. This should be set by the allocator of the
 49  *              device (i.e. the bus driver that discovered the device).
 50  *
 51  * At the lowest level, every device in a Linux system is represented by an
 52  * instance of struct device. The device structure contains the information
 53  * that the device model core needs to model the system. Most subsystems,
 54  * however, track additional information about the devices they host. As a
 55  * result, it is rare for devices to be represented by bare device structures;
 56  * instead, that structure, like kobject structures, is usually embedded within
 57  * a higher-level representation of the device.
 58  */
 59 struct device {
 60         struct device           *parent;
 61 
 62         struct device_private   *p;
 63 
 64         struct kobject kobj;
 65         const char              *init_name; /* initial name of the device */
 66         const struct device_type *type;
 67 
 68         struct mutex            mutex;  /* mutex to synchronize calls to
 69                                          * its driver.
 70                                          */
 71 
 72         struct bus_type *bus;           /* type of bus device is on */
 73         struct device_driver *driver;   /* which driver has allocated this
 74                                            device */
 75         void            *platform_data; /* Platform specific data, device
 76                                            core doesn‘t touch it */
 77         struct dev_pm_info      power;
 78         struct dev_power_domain *pwr_domain;
 79 
 80 #ifdef CONFIG_NUMA
 81         int             numa_node;      /* NUMA node this device is close to */
 82 #endif
 83         u64             *dma_mask;      /* dma mask (if dma‘able device) */
 84         u64             coherent_dma_mask;/* Like dma_mask, but for
 85                                              alloc_coherent mappings as
 86                                              not all hardware supports
 87                                              64 bit addresses for consistent
 88                                              allocations such descriptors. */
 89 
 90         struct device_dma_parameters *dma_parms;
 91 
 92         struct list_head        dma_pools;      /* dma pools (if dma‘ble) */
 93 
 94         struct dma_coherent_mem *dma_mem; /* internal for coherent mem
 95                                              override */
 96         /* arch specific additions */
 97         struct dev_archdata     archdata;
 98 
 99         struct device_node      *of_node; /* associated device tree node */
100 
101         dev_t                   devt;   /* dev_t, creates the sysfs "dev" */
102 
103         spinlock_t              devres_lock;
104         struct list_head        devres_head;
105 
106         struct klist_node       knode_class;
107         struct class            *class;
108         const struct attribute_group **groups;  /* optional groups */
109 
110         void    (*release)(struct device *dev);
111 };

View Code

下面的是调用具体函数的sample：

文件名：platform_device_test.c

 1 #include <linux/init.h>
 2 #include <linux/module.h>
 3 #include <linux/platform_device.h>
 4 
 5 static  void leds_release(struct device *dev)
 6 {
 7     printk("leds_release
");
 8 }
 9 
10 struct platform_device platform_device_hello = {
11     .name = "my_code_led",
12     .id = -1,
13     .dev = {
14         .release = leds_release,
15     
16     }
17 };
18 
19 static int hello_init(void)
20 {
21     printk(KERN_EMERG "init 
");
22     platform_device_register(&platform_device_hello);
23         return 0;
24 }
25 
26 static void hello_exit(void)
27 {
28     platform_device_unregister(&platform_device_hello); //unregister会查找release，如果找不到会报错
29 }
30 
31 module_init(hello_init);
32 module_exit(hello_exit);
33 
34 MODULE_LICENSE("Dual BSD/GPL");
35 MODULE_AUTHOR("NANZH");

编译：

1 $ make
2 make -C /home/nan/iTOP4412/iTop4412_Kernel_3.0 M=/home/nan/iTOP4412/3 modules 
3 make[1]: Entering directory ‘/home/nan/iTOP4412/iTop4412_Kernel_3.0‘
4   CC [M]  /home/nan/iTOP4412/3/platform_device_test.o
5   Building modules, stage 2.
6   MODPOST 1 modules
7   CC      /home/nan/iTOP4412/3/platform_device_test.mod.o
8   LD [M]  /home/nan/iTOP4412/3/platform_device_test.ko
9 make[1]: Leaving directory ‘/home/nan/iTOP4412/iTop4412_Kernel_3.0‘

拷贝到开发板并查看

1 # insmod platform_device_test.ko 
2 [  544.778744] init 
3 # ls /sys/devices/
4 platform/ system/   virtual/  
5 # ls /sys/devices/platform/
6 my_code_led  ...

至此达到和设备注册一中的mach-itop4412.c中注册方法达到相同的结果。