为啥在/dev目录下不能生成spidev1.0的设备文件

Posted 2023-04-23

参考技术A 在Linux中只有字符设备才有设备号，设备号分为主设备号和次设备号，主设备号是为了区分不同类型的设备，次设备号是为了区分同一类型的不同设备。

说明：注意看c字符开头的文件是字符设备，所以都有主设备号（红框）以及次设备号（绿框）。

linux SPI驱动——spidev之deive

1.定义board设备

   1:  struct spi_board_info {

   2:      /* the device name and module name are coupled, like platform_bus;

   3:       * "modalias" is normally the driver name.

   4:       *

   5:       * platform_data goes to spi_device.dev.platform_data,

   6:       * controller_data goes to spi_device.controller_data,

   7:       * irq is copied too

   8:       */

   9:      char        modalias[SPI_NAME_SIZE];

  10:      const void    *platform_data;

  11:      void        *controller_data;

  12:      int        irq;

  13:   

  14:      /* slower signaling on noisy or low voltage boards */

  15:      u32        max_speed_hz;

  16:   

  17:   

  18:      /* bus_num is board specific and matches the bus_num of some

  19:       * spi_master that will probably be registered later.

  20:       *

  21:       * chip_select reflects how this chip is wired to that master;

  22:       * it‘s less than num_chipselect.

  23:       */

  24:      u16        bus_num;

  25:      u16        chip_select;

  26:   

  27:      /* mode becomes spi_device.mode, and is essential for chips

  28:       * where the default of SPI_CS_HIGH = 0 is wrong.

  29:       */

  30:      u8        mode;

  31:   

  32:      /* ... may need additional spi_device chip config data here.

  33:       * avoid stuff protocol drivers can set; but include stuff

  34:       * needed to behave without being bound to a driver:

  35:       *  - quirks like clock rate mattering when not selected

  36:       */

   1:  /* add by xuyonghong for test */

   2:  struct spi_board_info jz_spi0_board_info[]  = {

   3:      {

   4:          .modalias               =  "spidev",

   5:          .mode                     =  SPI_MODE_3,

   6:          .max_speed_hz           =  1000000,

   7:          .controller_data        =  (void *)GPIO_PB(2),

   8:          .bus_num                =  0,

   9:          .chip_select            =  0,

  10:      },

  11:  };

  12:  int jz_spi0_devs_size = ARRAY_SIZE(jz_spi0_board_info);

   1:  int __init

   2:  spi_register_board_info(struct spi_board_info const *info, unsigned n)

   3:  {

   4:      struct boardinfo *bi;

   5:      int i;

   6:   

   7:      bi = kzalloc(n * sizeof(*bi), GFP_KERNEL);

   8:      if (!bi)

   9:          return -ENOMEM;

  10:   

  11:      for (i = 0; i < n; i++, bi++, info++) {

  12:          struct spi_master *master;

  13:   

  14:          memcpy(&bi->board_info, info, sizeof(*info));

  15:          mutex_lock(&board_lock);

  16:          list_add_tail(&bi->list, &board_list);

  17:          /* 

  18:              如果master先注册，则执行spi_match_master_to_boardinfo匹配，

  19:              否则在master注册的时候匹配device 

  20:          */

  21:          list_for_each_entry(master, &spi_master_list, list)

  22:              spi_match_master_to_boardinfo(master, &bi->board_info);

  23:          mutex_unlock(&board_lock);

  24:      }

  25:   

  26:      return 0;

  27:  }

   1:  spi_register_board_info(jz_spi0_board_info, jz_spi0_devs_size);

 

总结：

1. list_add_tail(&bi->list, &board_list); 讲board添加在board_list

2.当master已经注册，则通过spi_match_master_to_boardinfo和spi_new_device创建spi device。