如何使用mpc8xxx_gpio.c设备驱动

Question

我是设备驱动程序开发的新手。我正在尝试访问 MPC837xERDB 评估板的 GPIO。

我已将其内核升级到 linux-2.6.28.9 并启用对 mpc8xxx_gpio.c 的支持。启动时，它成功检测到两个 gpio 控制器。

现在我的问题是如何使用它与 gpio 引脚进行通信？我是否必须修改 mpc8xxx_gpio.c 文件中的代码才能执行我想要使用 gpios 执行的任何操作，或者我可以使用标准 gpio API在内核中提供（gpio_request()/gpio_free()）。我也尝试了标准内核 API，但失败了。这是我的代码：

#include <linux/module.h>
#include <linux/errno.h>  /* error codes */
#include <linux/gpio.h>

static __init int sample_module_init(void)
{
  int ret;

  int i;
  for (i=1; i<32; i++) {
    ret = gpio_request(i, "Sample Driver");
    if (ret) {
      printk(KERN_WARNING "sample_driver: unable to request GPIO_PG%d\n", i);
      //return ret;
    }  
  }

  return 0;
}

static __exit void sample_module_exit(void)
{
  gpio_free(9);
}

MODULE_LICENSE("GPL");

module_init(sample_module_init);
module_exit(sample_module_exit);

它给出了以下 O/P：

[  617.075329] sample_driver: unable to request GPIO_PG1
[  617.080418] sample_driver: unable to request GPIO_PG2
[  617.085470] sample_driver: unable to request GPIO_PG3
[  617.090522] sample_driver: unable to request GPIO_PG4
[  617.095574] sample_driver: unable to request GPIO_PG5
[  617.100625] sample_driver: unable to request GPIO_PG6
[  617.105676] sample_driver: unable to request GPIO_PG7
[  617.110727] sample_driver: unable to request GPIO_PG8
[  617.115779] sample_driver: unable to request GPIO_PG9
[  617.120830] sample_driver: unable to request GPIO_PG10
[  617.125968] sample_driver: unable to request GPIO_PG11
[  617.131106] sample_driver: unable to request GPIO_PG12
[  617.136245] sample_driver: unable to request GPIO_PG13
[  617.141383] sample_driver: unable to request GPIO_PG14
[  617.146521] sample_driver: unable to request GPIO_PG15
[  617.151660] sample_driver: unable to request GPIO_PG16
[  617.156798] sample_driver: unable to request GPIO_PG17
[  617.161936] sample_driver: unable to request GPIO_PG18
[  617.167074] sample_driver: unable to request GPIO_PG19
[  617.172213] sample_driver: unable to request GPIO_PG20
[  617.177351] sample_driver: unable to request GPIO_PG21
[  617.182489] sample_driver: unable to request GPIO_PG22
[  617.187628] sample_driver: unable to request GPIO_PG23
[  617.192767] sample_driver: unable to request GPIO_PG24
[  617.197905] sample_driver: unable to request GPIO_PG25
[  617.203042] sample_driver: unable to request GPIO_PG26
[  617.208182] sample_driver: unable to request GPIO_PG27
[  617.213319] sample_driver: unable to request GPIO_PG28
[  617.218458] sample_driver: unable to request GPIO_PG29
[  617.223597] sample_driver: unable to request GPIO_PG30
[  617.228735] sample_driver: unable to request GPIO_PG31
[  617.233873] sample_driver: unable to request GPIO_PG32

有人可以给我提供示例代码或其他东西吗？实际上我正在尝试设置 GPIO 引脚号。 9 为低电平有效，因为它连接到板上的 LED。

Answer 1

您是否查看过 Documentation/gpio.txt在你的内核源代码中？

Answer 2

根据您的其他问题：

# ls /sys/class/gpio/ -la
drwxr-xr-x    4 root     root            0 Jan  1 00:00 .
drwxr-xr-x   24 root     root            0 Jan  1 00:00 ..
--w-------    1 root     root         4096 Jan  1 00:10 export
drwxr-xr-x    3 root     root            0 Jan  1 00:00 gpiochip192
drwxr-xr-x    3 root     root            0 Jan  1 00:00 gpiochip224
--w-------    1 root     root         4096 Jan  1 00:00 unexport

您有两块 GPIO 引脚。一个块从编号 192 开始，另一个块从编号 224 开始。在上面的代码中，您尝试请求 GPIO 0-31，但您的平台上不存在该编号。

您可以通过查看每个 gpiochip* 目录中的 ngpio 文件来了解每个块中有多少个 GPIO。