LINUX驱动之SPI子系统之五spi_device的创建流程

来源：互联网发布：qt编程软件编辑：程序博客网时间：2024/06/08 04:53

原文地址：http://fpcfjf.blog.163.com/blog/static/55469793201292593727739/

上回已经讲到了，scan_boardinfo调用spi_new_device来创建新的SPI设备，

1. struct spi_device spi_new_device(struct spi_master *master,

2. struct spi_board_info *chip)

3. {

4. struct spi_device *proxy;

5. int status;

6. proxy = spi_alloc_device(master);

7. if (!proxy)

8. return NULL;

10.

11. WARN_ON(strlen(chip->modalias) >= sizeof(proxy->modalias));

12. /初始化spi_device的各个字段/

13. proxy->chipchip_select = chip->chip_select;

14. proxy->max_speed_hz = chip->max_speed_hz;

15. proxy->mode = chip->mode;

16. proxy->irq = chip->irq;

17. /这里获得了spi_device的名字，这个modalias也是在我们移植时在mach-smdk2440.c中的s3c2410_spi0_board中设定的/

18. strlcpy(proxy->modalias, chip->modalias, sizeof(proxy->modalias));

19. proxy->dev.platform_data = (void ) chip->platform_data;

20. proxy->controller_data = chip->controller_data;

21. proxy->controller_state = NULL;

22. /主要完成将spi_device添加到内核/

23. status = spi_add_device(proxy);

24. if (status < 0) {

25. spi_dev_put(proxy);

26. return NULL;

27. }

28.

29.

30. return proxy;

31. }

下面来看分配spi_alloc_device的函数，主要完成了分配spi_device，并初始化spi->dev的一些字段。

[cpp] view plaincopy

1. struct spi_device spi_alloc_device(struct spi_master *master)

2. {

3. struct spi_device *spi;

4. struct device *dev = master->dev.parent;

5. if (!spi_master_get(master))

6. return NULL;

7. spi = kzalloc(sizeof *spi, GFP_KERNEL);

8. if (!spi) {

9. dev_err(dev, “cannot alloc spi_device\n”);

10. spi_master_put(master);

11. return NULL;

12. }

13. spi->master = master;

14. spi->dev.parent = dev;

15. /设置总线是spi_bus_type，下面会讲到spi_device与spi_driver是怎样match上的/

16. spi->dev.bus = &spi_bus_type;

17. spi->dev.release = spidev_release;

18. device_initialize(&spi->dev);

19. return spi;

20. }

下面来看分配的这个spi_device是怎样注册进内核的：

[cpp] view plaincopy

1. int spi_add_device(struct spi_device *spi)

2. {

3. static DEFINE_MUTEX(spi_add_lock);

4. struct device *dev = spi->master->dev.parent;

5. int status;

6. /*spi_device的片选号不能大于spi控制器的片选数/

7. if (spi->chip_select >= spi->master->num_chipselect) {

8. dev_err(dev, “cs%d >= max %d\n”,

9. spi->chip_select,

10. spi->master->num_chipselect);

11. return -EINVAL;

12. }

13. /这里设置是spi_device在Linux设备驱动模型中的name，也就是图中的spi0.0，而在/dev/下设备节点的名字是proxy->modalias中的名字/

14. dev_set_name(&spi->dev, ”%s.%u”, dev_name(&spi->master->dev),

15. spi->chip_select);

16. mutex_lock(&spi_add_lock);

17. /如果总线上挂的设备已经有这个名字，则设置状态忙碌，并退出/

18. if (bus_find_device_by_name(&spi_bus_type, NULL, dev_name(&spi->dev))

19. != NULL) {

20. dev_err(dev, “chipselect %d already in use\n”,

21. spi->chip_select);

22. status = -EBUSY;

23. goto done;

24. }

25. /对spi_device的时钟等进行设置/

26. status = spi->master->setup(spi);

27. if (status < 0) {

28. dev_err(dev, “can’t %s %s, status %d\n”,

29. “setup”, dev_name(&spi->dev), status);

30. goto done;

31. }

32. /添加到内核/

33. status = device_add(&spi->dev);

34. if (status < 0)

35. dev_err(dev, “can’t %s %s, status %d\n”,

36. “add”, dev_name(&spi->dev), status);

37. else

38. dev_dbg(dev, “registered child %s\n”, dev_name(&spi->dev));

39.

40.

41. done:

42. mutex_unlock(&spi_add_lock);

43. return status;

44. }

45.

在上面的函数里调用了status = spi->master->setup(spi);大家在前边已经在s3c24xx_spi_probe看到，这个master->setup已经赋值为s3c24xx_spi_setup，所以看下面：

46. static int s3c24xx_spi_setup(struct spi_device spi)

47. {

48. 。。。。。。。。。。。。。。

49. ret = s3c24xx_spi_setupxfer(spi, NULL);

50. 。。。。。。。。。。。。。。

51. }

52.

53.

54. static int s3c24xx_spi_setupxfer(struct spi_device *spi,

55. struct spi_transfer *t)

56. {

57. struct s3c24xx_spi *hw = to_hw(spi);

58. unsigned int bpw;

59. unsigned int hz;

60. unsigned int div;

61. /设置了每字长的位数，发送速度/

62. bpw = t ? t->bits_per_word : spi->bits_per_word;

63. hz = t ? t->speed_hz : spi->max_speed_hz;

64.

65.

66. if (bpw != 8) {

67. dev_err(&spi->dev, “invalid bits-per-word (%d)\n”, bpw);

68. return -EINVAL;

69. }

70. /设置分频值/

71. div = clk_get_rate(hw->clk) / hz;

72.

73.

74. / is clk = pclk / (2 (pre+1)), or is it

75. clk = (pclk 2) / ( pre + 1) /

76.

77.

78. div /= 2;

79.

80.

81. if (div > 0)

82. div -= 1;

83.

84.

85. if (div > 255)

86. div = 255;

87.

88.

89. dev_dbg(&spi->dev, “setting pre-scaler to %d (hz %d)\n”, div, hz);

90. writeb(div, hw->regs + S3C2410_SPPRE);

91.

92.

93. spin_lock(&hw->bitbang.lock);

94. if (!hw->bitbang.busy) {

95. hw->bitbang.chipselect(spi, BITBANG_CS_INACTIVE);

96. / need to ndelay for 0.5 clocktick ? /

97. }

98. spin_unlock(&hw->bitbang.lock);

99.

100.

101. return 0;

102.}

驱动通过spi_new_device调用spi_alloc_device和spi_add_device两个函数，最后通过device_add将新建立的设备注册到内核上。

今天讲了设备，明天该driver驱动了，以及驱动如何与设备勾搭上。

慢慢来，要淡定。

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