I2C ext_flag解析

关于I2C 传输前，通常会遇到这样的设置：

struct i2c_client * client;

client->ext_flag = client->ext_flag | I2C_DMA_FLAG;

ret = i2c_master_send(client,pData,lens);

......

i2c传输前需要对 client->ext_flag 做设定，或上相关标志，各个flag解释如下：

 ▪I2C_DMA_FLAG

–开启DMA传输,default 为fifo mode传输

▪I2C_WR_FLAG

 –Enable write and read tranfer mode, Must set I2C_RS_FLAG ,Don’t support in DMA mode

▪I2C_RS_FLAG  

 –Enable REPEATED-START

▪I2C_HS_FLAG 

–Enable high speed mode,default 为低速和快速

 ▪I2C_PUSHPULL_FLAG

–使能pushpull mode,default 为open drain

▪I2C_ENEXT_FLAG 

–Allows slaves to hold the SCL line low if it is not yet ready for further processing ，Open open-drain mode of the SCL line

遇到标志：

client->ext_flag = client->ext_flag | I2C_A_FILTER_MSG;

其中该标记作用是移除i2c ack error。定义路径：工程代码/kernel/include/linux/i2c.h

#define I2C_A_FILTER_MSG    0x8000    /* filer out error messages    */
#define I2C_A_CHANGE_TIMING    0x4000    /* change timing paramters    */
#define I2C_MASK_FLAG    (0x00ff)
#define I2C_DMA_FLAG    (0x2000)
#define I2C_WR_FLAG        (0x1000)
#define I2C_RS_FLAG        (0x0800)
#define I2C_HS_FLAG   (0x0400)
#define I2C_ENEXT_FLAG (0x0200)
#define I2C_DISEXT_FLAG (0x0000)
#define I2C_POLL_FLAG (0x4000)
#define I2C_CH2_FLAG    (0x8000)

#define I2C_POLLING_FLAG (0x00000001)
#define I2C_PUSHPULL_FLAG (0x00000002)
#define I2C_3DCAMERA_FLAG (0x00000004)
#define I2C_DIRECTION_FLAG (0x00000008)