名侦探柯南经典剧集:Linux中的IO使用方法

Linux中的IO使用方法
应该是新版本内核才有的方法。
请参考：./Documentation/gpio.txt文件

提供的API：
驱动需要包含 #include
 
判断一个IO是否合法：int gpio_is_valid(int number);

设置GPIO的方向，如果是输出同时设置电平：
/* set as input or output, returning 0 or negative errno */
        int gpio_direction_input(unsigned gpio);
        int gpio_direction_output(unsigned gpio, int value);

获取输入引脚的电平：
/* GPIO INPUT: return zero or nonzero */
        int gpio_get_value(unsigned gpio);

        /* GPIO OUTPUT */
        void gpio_set_value(unsigned gpio, int value);

int gpio_cansleep(unsigned gpio);

To access such GPIOs, a different set of accessors is defined:

        /* GPIO INPUT: return zero or nonzero, might sleep */
        int gpio_get_value_cansleep(unsigned gpio);

        /* GPIO OUTPUT, might sleep */
        void gpio_set_value_cansleep(unsigned gpio, int value);

获取一个GPIO并声明标签：
/* request GPIO, returning 0 or negative errno.
         * non-null labels may be useful for diagnostics.
         */
        int gpio_request(unsigned gpio, const char *label);

        /* release previously-claimed GPIO */
        void gpio_free(unsigned gpio);

将GPIO映射为IRQ中断：
/* map GPIO numbers to IRQ numbers */
        int gpio_to_irq(unsigned gpio);

        /* map IRQ numbers to GPIO numbers (avoid using this) */
        int irq_to_gpio(unsigned irq);

设置GPIO IRQ中断类型：

if (!sw->both_edges) {
  if (gpio_get_value(sw->gpio))

       set_irq_type(gpio_to_irq(sw->gpio), IRQ_TYPE_EDGE_FALLING);
  else

   set_irq_type(gpio_to_irq(sw->gpio), IRQ_TYPE_EDGE_RISING);

在驱动中使用延时函数mdelay，需要包含文件。

1. #ifndef __LINUX_GPIO_H
   
2. #define __LINUX_GPIO_H
   
3. 
   
4. /* see Documentation/gpio.txt */
   
5. 
   
6. #ifdef CONFIG_GENERIC_GPIO
   
7. #include
   
8. 
   
9. #else
   
10. 
    
11. #include
    
12. #include
    
13. #include
    
14. 
    
15. struct device;
    
16. 
    
17. .......
18. 实现了一些与GENERIC_GPIO类型的gpio接口函数同样声明的空函数。
19. .......
    
20. 
    
21. #endif
    
22. 
    
23. #endif /* __LINUX_GPIO_H */

1. #ifndef _ARCH_ARM_GPIO_H
   
2. #define _ARCH_ARM_GPIO_H
   
3. 
   
4. /* not all ARM platforms necessarily support this API ... */
   
5. #include
   
6. 
   
7. #endif /* _ARCH_ARM_GPIO_H */

1. /* arch/arm/mach-s3c2410/include/mach/gpio.h
   
2.  *
   
3.  * Copyright (c) 2008 Simtec Electronics
   
4.  *    http://armlinux.simtec.co.uk/
   
5.  *    Ben Dooks
   
6.  *
   
7.  * S3C2410 - GPIO lib support
   
8.  *
   
9.  * This program is free software; you can redistribute it and/or modify
   
10.  * it under the terms of the GNU General Public License version 2 as
    
11.  * published by the Free Software Foundation.
    
12. */
    
13. 
    
14. #define gpio_get_value    __gpio_get_value
    
15. #define gpio_set_value    __gpio_set_value
    
16. #define gpio_cansleep    __gpio_cansleep
    
17. #define gpio_to_irq    __gpio_to_irq
    
18. 
    
19. /* some boards require extra gpio capacity to support external
    
20.  * devices that need GPIO.
    
21.  */
    
22. 
    
23. #ifdef CONFIG_CPU_S3C244X
    
24. #define ARCH_NR_GPIOS    (32 * 9 + CONFIG_S3C24XX_GPIO_EXTRA)  
    
25. #else
    
26. #define ARCH_NR_GPIOS    (256 + CONFIG_S3C24XX_GPIO_EXTRA)
    
27. #endif
    
28. 
    
29. #include
    
30. #include
    
31. #include
    
32. 
    
33. #ifdef CONFIG_CPU_S3C24XX
    
34. #define S3C_GPIO_END    (S3C2410_GPIO_BANKJ + 32)
    
35. #else
    
36. #define S3C_GPIO_END    (S3C2410_GPIO_BANKH + 32)
    
37. #endif

include/asm-generic/gpio.h，这个文件的内容不完全列出来。该文件涉及到了一个宏：CONFIG_GPIOLIB。会对GPIO接口函数的实现产生影响。

1. #include
   
2. 
   
3. #include
   
4. 
   
5. #include
6. 
   
7. #ifdef CONFIG_GPIOLIB
   
8. #include
   
9. /* Platforms may implement their GPIO interface with library code,
   
10.  * at a small performance cost for non-inlined operations and some
    
11.  * extra memory (for code and for per-GPIO table entries).
    
12.  *
    
13.  * While the GPIO programming interface defines valid GPIO numbers
    
14. 
    
15.  * to be in the range 0..MAX_INT, this library restricts them to the
    
16. 
    
17.  * smaller range 0..ARCH_NR_GPIOS-1.
    
18. 
    
19.  */
    
20. 
    
21. 
    
22. #ifndef ARCH_NR_GPIOS
    
23. #define ARCH_NR_GPIOS 256
    
24. #endif
25. 
    
26. static inline int gpio_is_valid(int number) ----用于判断GPIO号是否可用。
    
27. {
    
28.     /* only some non-negative numbers are valid */
    
29.     return ((unsigned)number) < ARCH_NR_GPIOS;
    
30. }
31. 
    
32. struct device;
    
33. struct seq_file;
    
34. struct module;
    
35. .......
    
36. 一些函数声明，宏定义。
    
37. .......
    
38. #else /* !CONFIG_HAVE_GPIO_LIB */
    
39. static inline int gpio_is_valid(int number)
    
40. {
    
41.  /* only non-negative numbers are valid */
    
42.  return number >= 0;
    
43. }
    
44. /* platforms that don't directly support access to GPIOs through I2C, SPI,
    
45.  * or other blocking infrastructure can use these wrappers.
    
46.  */
    
47. static inline int gpio_cansleep(unsigned gpio)
    
48. {
    
49.  return 0;
    
50. }
    
51. static inline int gpio_get_value_cansleep(unsigned gpio)
    
52. {
    
53.  might_sleep();
    
54.  return gpio_get_value(gpio);
    
55. }
    
56. static inline void gpio_set_value_cansleep(unsigned gpio, int value)
    
57. {
    
58.  might_sleep();
    
59.  gpio_set_value(gpio, value);
    
60. }
    
61. #endif /* !CONFIG_HAVE_GPIO_LIB */