linux SPI驱动——gpio模拟spi驱动（转载）

一：首先在我的平台注册platform_device，保证能让spi-gpio.c能执行到probe函数。

   1:  struct spi_gpio_platform_data {
   2:      unsigned    sck;
   3:      unsigned    mosi;
   4:      unsigned    miso;
   5:
   6:      u16        num_chipselect;
   7:  };

   1:  //#define NCS      GPIO_PB(2)                     //定义SS所对应的GPIO接口编号
   2:  //#define SCLK     GPIO_PB(0)                     //定义SCLK所对应的GPIO接口编号
   3:  //#define MOSI     GPIO_PB(4)                     //定义SCLK所对应的GPIO接口编号
   4:  //#define MISO     GPIO_PB(1)
   5:  static struct spi_gpio_platform_data jz_spi_gpio_data = {
   6:      .sck    = GPIO_PB(0),    //GPIO_SPI_SCK,
   7:      .mosi    = GPIO_PB(4),     //GPIO_SPI_MOSI,
   8:      .miso    = GPIO_PB(1),    //GPIO_SPI_MISO,
   9:      .num_chipselect = 1,
  10:  };
  11:
  12:  struct platform_device jz_spi_gpio_device = {
  13:      .name   = "spi_gpio",
  14:      .id     = 0,
  15:      .dev    = {
  16:          .platform_data = &jz_spi_gpio_data,
  17:      },
  18:  };

注册platform device

1: platform_device_register（&jz_spi_gpio_device);

二：注册platform_driver在spi_gpio.c里面注册platform driver

   1:  MODULE_ALIAS("platform:" DRIVER_NAME);
   2:
   3:  static struct platform_driver spi_gpio_driver = {
   4:      .driver.name    = DRIVER_NAME,
   5:      .driver.owner    = THIS_MODULE,
   6:      .remove        = __exit_p(spi_gpio_remove),
   7:  };
   8:
   9:  static int __init spi_gpio_init(void)
  10:  {
  11:      return platform_driver_probe(&spi_gpio_driver, spi_gpio_probe);
  12:  }
  13:  module_init(spi_gpio_init);
  14:
  15:  static void __exit spi_gpio_exit(void)
  16:  {
  17:      platform_driver_unregister(&spi_gpio_driver);
  18:  }
  19:  module_exit(spi_gpio_exit);
  20:
  21:
  22:  MODULE_DESCRIPTION("SPI master driver using generic bitbanged GPIO ");
  23:  MODULE_AUTHOR("David Brownell");
  24:  MODULE_LICENSE("GPL");

 

三：具体算法分析

   1:  struct spi_gpio {

   2:      struct spi_bitbang          bitbang;        /* gpio 模拟spi算法相关的结构 */

   3:      struct spi_gpio_platform_data  pdata;        /* spi platform data 对应模拟spi的四个gpio编号 */

   4:      struct platform_device    *pdev;        /* 对应注册的 platform device */

   5:  };

   1:
   2:  static int __init spi_gpio_probe(struct platform_device *pdev)
   3:  {
   4:      int                status;
   5:      struct spi_master        *master;
   6:      struct spi_gpio            *spi_gpio;
   7:      struct spi_gpio_platform_data    *pdata;
   8:      u16 master_flags = 0;
   9:
  10:      pdata = pdev->dev.platform_data; /* 存放spi的四根gpio */
  11:  #ifdef GENERIC_BITBANG
  12:      if (!pdata || !pdata->num_chipselect)
  13:          return -ENODEV;
  14:  #endif
  15:
  16:      /* 申请注册四个gpio */
  17:      status = spi_gpio_request(pdata, dev_name(&pdev->dev), &master_flags);
  18:      if (status < 0) {
  19:          return status;
  20:      }
  21:
  22:      /* alloc a spi master ,master->dev->p->driver_data = &master[1]*/
  23:      master = spi_alloc_master(&pdev->dev, sizeof *spi_gpio);
  24:      if (!master) {
  25:          status = -ENOMEM;
  26:          goto gpio_free;
  27:      }
  28:      /* spi_gpio指向一块空间, 即指向mstaer[1]
  29:         pdev->dev->p->driver_data = spi_gpio;
  30:         初始化spi_gpio
  31:      */
  32:      spi_gpio = spi_master_get_devdata(master);
  33:      platform_set_drvdata(pdev, spi_gpio);
  34:
  35:      spi_gpio->pdev = pdev;
  36:      if (pdata)
  37:          spi_gpio->pdata = *pdata;
  38:
  39:      master->flags = master_flags;
  40:      master->bus_num = pdev->id;
  41:      master->num_chipselect = SPI_N_CHIPSEL;
  42:      master->setup = spi_gpio_setup; /* setup 比如cs引脚申请 */
  43:      master->cleanup = spi_gpio_cleanup;
  44:      /* spi_gpio->bitbang.master = master */
  45:      spi_gpio->bitbang.master = spi_master_get(master);
  46:      spi_gpio->bitbang.chipselect = spi_gpio_chipselect;
  47:      /* spi_gpio->bitbang.txrx_word 数组函数四个元素指针，分别指向spi四种mode算法函数 */
  48:      if ((master_flags & (SPI_MASTER_NO_TX | SPI_MASTER_NO_RX)) == 0) {
  49:          spi_gpio->bitbang.txrx_word[SPI_MODE_0] = spi_gpio_txrx_word_mode0;
  50:          spi_gpio->bitbang.txrx_word[SPI_MODE_1] = spi_gpio_txrx_word_mode1;
  51:          spi_gpio->bitbang.txrx_word[SPI_MODE_2] = spi_gpio_txrx_word_mode2;
  52:          spi_gpio->bitbang.txrx_word[SPI_MODE_3] = spi_gpio_txrx_word_mode3;
  53:      } else {
  54:          spi_gpio->bitbang.txrx_word[SPI_MODE_0] = spi_gpio_spec_txrx_word_mode0;
  55:          spi_gpio->bitbang.txrx_word[SPI_MODE_1] = spi_gpio_spec_txrx_word_mode1;
  56:          spi_gpio->bitbang.txrx_word[SPI_MODE_2] = spi_gpio_spec_txrx_word_mode2;
  57:          spi_gpio->bitbang.txrx_word[SPI_MODE_3] = spi_gpio_spec_txrx_word_mode3;
  58:      }
  59:      /* spi_gpio->bitbang.setup_transfer初始化传输的bits_per_word和speed */
  60:      spi_gpio->bitbang.setup_transfer = spi_bitbang_setup_transfer;
  61:      spi_gpio->bitbang.flags = SPI_CS_HIGH;
  62:      /* spi_gpio->bitbang相关算法接口初始化 */
  63:      status = spi_bitbang_start(&spi_gpio->bitbang);
  64:      if (status < 0) {
  65:          spi_master_put(spi_gpio->bitbang.master);
  66:  gpio_free:
  67:          if (SPI_MISO_GPIO != SPI_GPIO_NO_MISO)
  68:              gpio_free(SPI_MISO_GPIO);
  69:          if (SPI_MOSI_GPIO != SPI_GPIO_NO_MOSI)
  70:              gpio_free(SPI_MOSI_GPIO);
  71:          gpio_free(SPI_SCK_GPIO);
  72:          spi_master_put(master);
  73:      }
  74:
  75:      return status;
  76:  }

 

四：总之最终让spi_gpi0整个对象存放了整个gpio模拟spi的算法结构；而pdev->dev->p->driver_data = spi_gpio;

platform device和 platform driver两者match结果是：

root@CarRadio:/# ls /sys/bus/platform/devices/spi_gpio.0/ driver      modalias    power       spi0.0      spi_master  subsystem   uevent root@CarRadio:/# ls /sys/bus/platform/devices/spi_gpio.0/driver/ spi_gpio.0  uevent

 

转载自：https://www.cnblogs.com/xuyh/p/6025783.html