linux SPI驅動——gpio模擬spi驅動（三）

一：首先在個人平臺註冊platform_device，保證能讓spi-gpio.c能執行到probe函數。

 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) //定義SS所對應的GPIO接口編號 

 2: //#define SCLK GPIO_PB(0) //定義SCLK所對應的GPIO接口編號 

 3: //#define MOSI GPIO_PB(4) //定義SCLK所對應的GPIO接口編號 

 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: };

註冊platform device

1: platform_device_register（&jz_spi_gpio_device);

二：註冊platform_driver在spi_gpio.c裏面註冊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：具體算法分析

 1: struct spi_gpio {

 2:     struct spi_bitbang          bitbang;        /* gpio 模擬spi算法相關的結構 */

 3:     struct spi_gpio_platform_data  pdata;        /* spi platform data 對應模擬spi的四個gpio編號 */

 4:     struct platform_device    *pdev;        /* 對應註冊的 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:     /* 申請註冊四個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指向一塊空間, 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 好比cs引腳申請 */

 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 數組函數四個元素指針，分別指向spi四種mode算法函數 */

 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初始化傳輸的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相關算法接口初始化 */

 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：總之最終讓spi_gpi0整個對象存放了整個gpio模擬spi的算法結構；而pdev->dev->p->driver_data = spi_gpio;

platform device和 platform driver二者match結果是：

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