hacking a friend's Linux buzzer driver in OK335xS

 /****************************************************************************
  *          hacking a friend's Linux buzzer driver in OK335xS
  * 说明：
  *   解读朋友的Linux buzzer驱动，作为后续相关编码的参考。
  *
  *                                   2015-8-25 晴 深圳 南山平山村 曾剑锋
  ***************************************************************************/
 #include <linux/init.h>
 #include <linux/module.h>
 #include <linux/leds.h>
 #include <linux/io.h>
 #include <linux/semaphore.h>
 #include <linux/kernel.h>
 #include <linux/cdev.h>
 #include <linux/types.h>
 #include <linux/fs.h>
 #include <mach/gpio.h>
 #include <plat/mux.h>
 #include <linux/gpio.h>

 #define IO_VAULE_H          5
 #define IO_VAULE_L          6

 /**
  * 1. 参考文档：AM335x ARM Cortex-A8 Microprocessors (MPUs) Technical Reference Manual (Rev. H).pdf
  * 2. ARM Cortex-A8 Memory Map：
  *                         Table 2-1. L3 Memory Map (page 155)
  *  +------------+---------------------+-------------------+------------------+
  *  | Block Name | Start_address (hex) | End_address (hex) | Size Description |
  *  +------------+---------------------+-------------------=------------------+
  *  | L4_WKUP    | 0x44C0_0000         | 0x44FF_FFFF       | 4MB L4_WKUP      |
  *  +------------+---------------------+-------------------+------------------+
  *                        Table 2-2. L4_WKUP Peripheral Memory Map (page 158)
  *  +----------------+---------------------+-------------------+-------+--------------------------+
  *  | Region Name    | Start Address (hex) | End Address (hex) | Size  | Description              |
  *  +----------------+---------------------+-------------------+-------+--------------------------+
  *  | Control Module | 0x44E1_0000         | 0x44E1_1FFF       | 128KB | Control Module Registers |
  *  +----------------+---------------------+-------------------+-------+--------------------------+
  */
 #define Control_Module_address                0x44E10000

 /**
  * 1. 参考文档：AM335x ARM Cortex-A8 Microprocessors (MPUs) Technical Reference Manual (Rev. H).pdf
  * 2. CONTROL_MODULE Registers：
  *                     Table 9-10. CONTROL_MODULE REGISTERS
  *  +--------+---------------+----------------------+----------------+
  *  | Offset | Acronym       | Register Description | Section        |
  *  +--------+---------------+----------------------+----------------+
  *  | 960h   | conf_spi0_cs1 |                      | Section 9.3.51 |
  *  +--------+---------------+----------------------+----------------+
  */
 #define CONFIG_SPI0_CS1_offset                0x960

 /**
  * can't find any reference for this define, but it can use
  */
 #define GPIO_TO_PIN(bank, gpio) (32 * (bank) + (gpio) )

 /**
  * just like container_of in kernel
  */
 #define GET_STRUCT_ADDR (ptr,type,member)\
      ((unsigned long )ptr - (unsigned long)((type*)->member)) 

 /**
  * 1. 参考文档：Sitara AM335x ARM Cortex-A8 Microprocessors (MPUs) (Rev. F).pdf
  *    Table 2-7. Ball Characteristics (ZCE and ZCZ Packages) (continued) (page 43)
  *  +-----------+-----------+-------------+--------------------+---------+---------+
  *  | ZCE BALL  | ZCZ BALL  | PIN NAME[2] |  SIGNAL NAME[3]    | MODE[4] | TYPE[5] |
  *  | NUMBER[1] | NUMBER[1] |             |                    |         |         |
  *  +-----------+-----------+-------------+--------------------+---------+---------+
  *  | B16       | C15       | SPI0_CS1    |  spi0_cs1          | 0       | I/O     |
  *  |           |           |             |--------------------|---------+---------+
  *  |           |           |             |  uart3_rxd         | 1       | I       |
  *  |           |           |             |--------------------|---------+---------+
  *  |           |           |             |  eCAP1_in_PWM1_out | 2       | I/O     |
  *  |           |           |             |--------------------|---------+---------+
  *  |           |           |             |  mmc0_pow          | 3       | O       |
  *  |           |           |             |--------------------|---------+---------+
  *  |           |           |             |  xdma_event_intr2  | 4       | I       |
  *  |           |           |             |--------------------|---------+---------+
  *  |           |           |             |  mmc0_sdcd         | 5       | I       |
  *  |           |           |             |--------------------|---------+---------+
  *  |           |           |             |  EMU4              | 6       | I/O     |
  *  |           |           |             |--------------------|---------+---------+
  *  |           |           |             |  gpio0_6           | 7       | I/O     |
  *  +-----------+-----------+-------------+--------------------+---------+---------+
  */
 #define BUZZER_PIN     GPIO_TO_PIN(0, 6)

 struct cdev * buzz;

 static int buzz_init(void)
 {
     int result;

     /**
      * void *ioremap(unsigned long phys_addr, unsigned long size)
      *  入口：phys_addr：要映射的起始的IO地址；
      *  size：要映射的空间的大小；
      */
     void __iomem * base = ioremap(Control_Module_address, 0x1FFF);
     /**
      * 1 参考文章：AM335x ARM Cortex-A8 Microprocessors (MPUs) Technical Reference Manual (Rev. H).pdf
      *          Table 9-61. conf_<module>_<pin> Register Field Descriptions（page 815）
      *  +-------+-------------------------+--------------+-------------------------------------------+
      *  | Bit   | Field                   | Type | Reset | Description                               |
      *  +-------+-------------------------+--------------+-------------------------------------------+
      *  | 31-20 | Reserved                | R    | 0h    |                                           |
      *  +-------+-------------------------+--------------+-------------------------------------------+
      *  | 19-7  | Reserved                | R    | 0h    |                                           |
      *  +-------+-------------------------+--------------+-------------------------------------------+
      *  | 6     | conf_<module>_<pin>_sle | R/W  | X     | Select between faster or slower slew rate |
      *  |       | wctrl                   |      |       | 0: Fast                                   |
      *  |       |                         |      |       | 1: Slow                                   |
      *  |       |                         |      |       | Reset value is pad-dependent.             |
      *  +-------+-------------------------+--------------+-----------------------------------------  +
      *  | 5     | conf_<module>_<pin>_rx  | R/W  | 1h    | Input enable value for the PAD            |
      *  |       | active                  |      |       | 0: Receiver disabled                      |
      *  |       |                         |      |       | 1: Receiver enabled                       |
      *  +-------+-------------------------+--------------+-----------------------------------------  +
      *  | 4     | conf_<module>_<pin>_pu  | R/W  | X     | Pad pullup/pulldown type selection        |
      *  |       | typesel                 |      |       | 0: Pulldown selected                      |
      *  |       |                         |      |       | 1: Pullup selected                        |
      *  |       |                         |      |       | Reset value is pad-dependent.             |
      *  +-------+-------------------------+--------------+-------------------------------------------+
      *  | 3     | conf_<module>_<pin>_pu  | R/W  | X     | Pad pullup/pulldown enable                |
      *  |       | den                     |      |       | 0: Pullup/pulldown enabled                |
      *  |       |                         |      |       | 1: Pullup/pulldown disabled               |
      *  |       |                         |      |       | Reset value is pad-dependent.             |
      *  +-------+-------------------------+--------------+-------------------------------------------+
      *  | 2-0   | conf_<module>_<pin>_m   | R/W  | X     | Pad functional signal mux select.         |
      *  |       | mode                    |      |       | Reset value is pad-dependent.             |
      *  +-------+-------------------------+--------------+-------------------------------------------+
      * 2. 0x37 = B0011 0111
      *      1. bit 6 --> 0 --> Fast;
      *      2. bit 5 --> 1 --> Receiver enabled;
      *      3. bit 4 --> 1 --> Pullup selected;
      *      4. bit 3 --> 0 --> Pullup/pulldown enabled;
      *      5. bit 2-0 --> 7 --> gpio0_6;  参考前面说明 #define BUZZER_PIN     GPIO_TO_PIN(0,6)
      */
     __raw_writel(0x37, (base + CONFIG_SPI0_CS1_offset ));

     /* Allocating GPIOs and setting direction */
     result = gpio_request(BUZZER_PIN, "buzzer");            //usr1
     if (result != )
         printk("gpio_request(0_6) failed!\n"); return result; 

     result = gpio_direction_output(BUZZER_PIN, );
     if (result != )
         printk("gpio_direction(0_6) failed!\n"); return result; 

     gpio_set_value(BUZZER_PIN, );

     return result;
 }

 static int buzz_open(struct inode *inode, struct file *file)
 {
     return ;
 }

 static ssize_t buzz_read (struct file *file, char __user *buf, size_t size, loff_t * off)
 {
     return ;
 }

 static int buzz_ioctl(struct file *filp,unsigned int cmd,    unsigned long arg)
 {
     if(cmd == IO_VAULE_H ) {
         printk(" buzz iotcl IO_VALUE_H.\n");       // for debug
             gpio_set_value(BUZZER_PIN,);
     }
     if(cmd == IO_VAULE_L ) {
         printk(" buzz iotcl IO_VALUE_L.\n");
             gpio_set_value(BUZZER_PIN,);
     }

     return ;
 }

 static ssize_t buzz_write (struct file *file, char __user *buf, size_t size, loff_t * off)
 {
     return ;
 }

 static int buzz_release (struct inode *inode, struct file *file)
 {
     return ;
 }

 struct file_operations buzz_fops = {
     .owner = THIS_MODULE,
     .open =    buzz_open,
     .read =    buzz_read,
     .write =   buzz_write,
     .release = buzz_release,
     .unlocked_ioctl= buzz_ioctl
 };

 static int __init  buzzm_init()
 {
     /**
      * 表示静态的申请和注册设备号:
      * register_chrdev_region(dev_t first,unsigned int count,char *name)
      *    first :要分配的设备编号范围的初始值(次设备号常设为0);
      *    count:连续编号范围.
      *    name:编号相关联的设备名称. (/proc/devices);
      */
     if(register_chrdev_region(MKDEV(,),,"aple_buzz") < )
         return     -ENOMEM    ;

     /**
      * 前面只是注册了设备号，后面要向内核添加设备了；
      */
     buzz = cdev_alloc();
     if(buzz == NULL)
         return -ENOMEM;

     cdev_init(buzz , &buzz_fops);
     cdev_add(buzz ,MKDEV(,),);
     buzz_init();
     return ;
 }

 static void  __exit  buzzm_exit()
 {
     cdev_del(buzz);
     unregister_chrdev_region(MKDEV(,),);
 }

 module_init(buzzm_init);
 module_exit(buzzm_exit);
 MODULE_AUTHOR("Danny Zhao");
 MODULE_LICENSE("GPL");