Android之GPS研究


TI平台使用SIRF GPS 1.底层驱动的实现 GPS厂商提供的库通过echo sysfs的方式控制gps的onoff和reset，这需要linux实现GPS的sysfs模型驱动，在driver文件夹中增加gps.c文件 （1）填充一个bin_attribute的结构体，驱动加载后就会在系统的/sys/module目录下创建sirf文件
  1. static struct bin_attribute sirf_mode_attr = {
  2.     .attr = {
  3.         .name = "sirf",
  4.         .owner = THIS_MODULE,
  5.         .mode = S_IRUGO | S_IWUGO,
  6.     },
  7.     .size = 0,
  8.     .read = readcmd,
  9.     .write = writecmd,
  10. };
（2）probe函数
  1. static int __init gps_probe(struct platform_device *pdev)
  2. {    
  3.     int ret;
  4.     ret = sysfs_create_bin_file(&(module_kset->kobj), &sirf_mode_attr);
  5.     if (ret) {
  6.             printk(KERN_ERR "<SiRF> Failed to create sys file\n");
  7.         return -ENOMEM;
  8.     }
  9.     return 0;
  10. }

（3）remove函数

  1. static int __init gps_remove(struct platform_device *pdev)
  2. {
  3.     sysfs_remove_bin_file(&(module_kset->kobj), &sirf_mode_attr);

  5.     return 0;
  6. }

（4）平台驱动的注册

  1. static struct platform_driver gps_driver = {
  2.     .probe        = gps_probe,
  3.     .remove        = gps_remove,
  4.     .driver        = {
  5.         .name    = "gps",
  6.     },
  7. };

  9. static int __init gps_init(void)
  10. {
  11.     return platform_driver_register(&gps_driver);
  12. }

  14. static void __exit gps_exit(void)
  15. {
  16.     platform_driver_unregister(&gps_driver);
  17. }

  19. late_initcall(gps_init);
  20. module_exit(gps_exit);

（5）write和read函数（read暂时为空，没有用到）

  1. static ssize_t readcmd(struct kobject *kobj,
  2.             struct bin_attribute *attr,
  3.             char *buf, loff_t off, size_t count)
  4. {
  5. }

  7. static ssize_t writecmd(struct kobject *kobj,
  8.             struct bin_attribute *attr,
  9.             char *buf, loff_t off, size_t count)
  10. {
  11.     char *tail;
  12.     int op;
  13.     op = simple_strtol(buf, &tail, 10);
  14.     switch(op) {
  15.         case 1:
  16.         case 2:
  17.             break;
  18.         case 3:
  19.             printk(KERN_BUG "<SiRF> Chip running...\n");
  20.             set_power_on();            
  21.             run_mode = RUN_MODE;             
  22.             break;
  23.         case 4:
  24.             printk(KERN_BUG "<SiRF> Chip stopped...\n");
  25.             set_power_off();
  26.             run_mode = STOP_MODE;
  27.             break;
  28.         case 5:
  29.             printk(KERN_BUG "<SiRF> Chip reset on high...\n");
  30.             set_reset(1);        
  31.             break;
  32.         case 6:
  33.             printk(KERN_BUG "<SiRF> Chip reset on low...\n");
  34.             set_reset(0);
  35.             break;
  36.         default:
  37.             printk(KERN_BUG "<SiRF> Unknown operation %d\n", op);
  38.             break;
  39.     }
  40.     return count;
  41. }

现在通过echo number > /sys/module/sirf就能控制GPS的power on/off和reset。

  • 1
  • 2
  • 下一页

相关内容