和菜鳥一起學linux總線驅動之初識spi驅動主要結構

?????? 既然知道了協議了，那么就可以開始去瞧瞧linux kenerl中的spi的驅動代碼了，代碼中有很多的結構體，還是對主要的結構體先做個了解吧，那樣才可以很好的理解驅動。主要是include/linux/spi.h

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首先是SPI的主機和從機通信接口，也就是SPI總線，

extern struct bus_type spi_bus_type;

bus_type定義在linux/device.h中

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struct bus_type {const char              *name;     //總線的名字struct bus_attribute *bus_attrs;struct device_attribute    *dev_attrs;struct driver_attribute    *drv_attrs; //總線上的device和driver的匹配，匹配成功返回非0值int (*match)(struct device *dev, struct device_driver *drv);int (*uevent)(struct device *dev, struct kobj_uevent_env *env);//當新的device或driver加到總線上的時候，調用driver中的probe函數經行匹配int (*probe)(struct device *dev);int (*remove)(struct device *dev);void (*shutdown)(struct device *dev);int (*suspend)(struct device *dev, pm_message_t state);int (*resume)(struct device *dev);const struct dev_pm_ops *pm;struct subsys_private *p;
};

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SPI設備

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struct spi_device {struct device          dev;struct spi_master    *master;    //SPI控制器u32                max_speed_hz;  //最大時鐘頻率u8                  chip_select;     //片選u8                  mode;          //SPI模式
#define    SPI_CPHA     0x01                     /* clock phase */
#define    SPI_CPOL     0x02                     /* clock polarity */
#define    SPI_MODE_0       (0|0)                     /* (original MicroWire) */
#define    SPI_MODE_1       (0|SPI_CPHA)
#define    SPI_MODE_2       (SPI_CPOL|0)
#define    SPI_MODE_3       (SPI_CPOL|SPI_CPHA)
#define    SPI_CS_HIGH      0x04                     /* chipselect active high? */
#define    SPI_LSB_FIRST    0x08                     /* per-word bits-on-wire */
#define    SPI_3WIRE   0x10                     /* SI/SO signals shared */
#define    SPI_LOOP     0x20                     /* loopback mode */
#define    SPI_NO_CS   0x40                     /* 1 dev/bus, no chipselect */
#define    SPI_READY  0x80                     /* slave pulls low to pause */u8                  bits_per_word;              //一次傳輸的bits，可以是8、16、32，默認是8int                 irq;                 void               *controller_state;void               *controller_data;        char               modalias[SPI_NAME_SIZE];  //別名，用于device和driver的匹配
};

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SPI驅動

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struct spi_driver {const struct spi_device_id *id_table;int                 (*probe)(struct spi_device *spi);  //綁定驅動和SPI設備int                 (*remove)(struct spi_device *spi);void               (*shutdown)(struct spi_device *spi);int                 (*suspend)(struct spi_device *spi, pm_message_t mesg);int                 (*resume)(struct spi_device *spi);struct device_driver         driver;
};

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SPI主控制器

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struct spi_master {struct device   dev;   //驅動的設備接口struct list_head list;        //SPI控制器的鏈表頭s16                bus_num;    //總線號/* chipselects will be integral to many controllers; some others* might use board-specific GPIOs.*/u16                num_chipselect;    //SPI設備的片選號u16                dma_alignment;     //dma模式  /* spi_device.mode flags understood by this controller driver */u16                mode_bits;         /* other constraints relevant to this driver */u16                flags;#define SPI_MASTER_HALF_DUPLEX    BIT(0)           /* can't do full duplex */
#define SPI_MASTER_NO_RX   BIT(1)           /* can't do buffer read */
#define SPI_MASTER_NO_TX    BIT(2)           /* can't do buffer write *//* lock and mutex for SPI bus locking */spinlock_t              bus_lock_spinlock;struct mutex           bus_lock_mutex;bool               bus_lock_flag;int                 (*setup)(struct spi_device *spi);   //更新SPI設備的模式和SPI設備的采樣時鐘int                 (*transfer)(struct spi_device *spi,    //添加一個消息到控制器的傳輸隊列struct spi_message *mesg);void               (*cleanup)(struct spi_device *spi);};

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SPI傳輸

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struct spi_transfer {/* it's ok if tx_buf == rx_buf (right?)* for MicroWire, one buffer must be null* buffers must work with dma_*map_single() calls, unless*   spi_message.is_dma_mapped reports a pre-existing mapping*/const void       *tx_buf;    //要寫的數據void        *rx_buf;                //要讀的數據unsigned  len;                       //數據長度dma_addr_t    tx_dma;       //tx_buf的DMA地址dma_addr_t    rx_dma;         //rx_buf的DMA地址unsigned  cs_change:1;u8           bits_per_word;       //傳輸的bytes數，不選就用默認的u16         delay_usecs;                  //微秒延時，用以傳輸數據后，改變片選信號前u32         speed_hz;            //傳輸速率，不選就用默認的struct list_head transfer_list;     //傳輸鏈表，用以傳輸spi_message};

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SPI消息

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struct spi_message {struct list_head       transfers;   // struct spi_device     *spi;      //加到傳輸隊列中的spi設備unsigned         is_dma_mapped:1;   //DMA傳輸控制位/* completion is reported through a callback */void               (*complete)(void *context);      //傳輸完成void               *context;                                    //complete函數的參數                unsigned         actual_length;             //所有成功傳輸字段的總長度int                 status;                                 //傳輸成功返回0，否則返回錯誤/* for optional use by whatever driver currently owns the* spi_message ...  between calls to spi_async and then later* complete(), that's the spi_master controller driver.*/struct list_head       queue;void               *state;};

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SPI bitbang

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struct spi_bitbang {struct workqueue_struct *workqueue;struct work_struct   work;spinlock_t              lock;struct list_head       queue;u8                  busy;u8                  use_dma;u8                  flags;             /* extra spi->mode support */struct spi_master    *master;/* setup_transfer() changes clock and/or wordsize to match settings* for this transfer; zeroes restore defaults from spi_device.*/int   (*setup_transfer)(struct spi_device *spi,struct spi_transfer *t);void (*chipselect)(struct spi_device *spi, int is_on);
#define    BITBANG_CS_ACTIVE      1     /* normally nCS, active low */
#define    BITBANG_CS_INACTIVE   0/* txrx_bufs() may handle dma mapping for transfers that don't* already have one (transfer.{tx,rx}_dma is zero), or use PIO*/int   (*txrx_bufs)(struct spi_device *spi, struct spi_transfer *t);/* txrx_word[SPI_MODE_*]() just looks like a shift register */u32  (*txrx_word[4])(struct spi_device *spi,unsigned nsecs,u32 word, u8 bits);};

??????? 在SPI控制器里面最常用的用來處理傳輸的結構體spi_bitbang了。

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SPI borad info

struct spi_board_info {/* the device name and module name are coupled, like platform_bus;* "modalias" is normally the driver name.** platform_data goes to spi_device.dev.platform_data,* controller_data goes to spi_device.controller_data,* irq is copied too*/char  modalias[SPI_NAME_SIZE];const void *platform_data;void  *controller_data;int  irq;/* slower signaling on noisy or low voltage boards */u32  max_speed_hz;/* bus_num is board specific and matches the bus_num of some* spi_master that will probably be registered later.** chip_select reflects how this chip is wired to that master;* it's less than num_chipselect.*/u16  bus_num;u16  chip_select;/* mode becomes spi_device.mode, and is essential for chips* where the default of SPI_CS_HIGH = 0 is wrong.*/u8  mode;/* ... may need additional spi_device chip config data here.* avoid stuff protocol drivers can set; but include stuff* needed to behave without being bound to a driver:*  - quirks like clock rate mattering when not selected*/
};

?????? 控制器里會讀取borad info里的參數

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SPI gpio_platform_data

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struct spi_gpio_platform_data {unsigned  sck;unsigned  mosi;unsigned  miso;u16         num_chipselect;};

??????? 因為我用的比較多的是GPIO模擬的，所以還是記錄下這個從platform傳進來的管腳號。

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?????? OK，對于SPI用到的結構體基本上已經介紹完了，那么接下來就介紹其主要函數了。

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