#include <hw/i2c.h> #define DCMD_I2C_SENDRECV __DIOTF(_DCMD_I2C, 7, i2c_sendrecv_t)
The arguments to devctl() are:
Argument | Value |
---|---|
filedes | A file descriptor that you obtained by opening the device. |
dcmd | DCMD_I2C_SENDRECV |
dev_data_ptr | A pointer to a i2c_sendrecv_t that's followed by a buffer |
n_bytes | sizeof(i2c_sendrecv_t) plus the size of the buffer |
dev_info_ptr | NULL |
The DCMD_I2C_SENDRECV command executes a send followed by a receive. This sequence is typically used to read a slave device's register value. When multiple applications access the same slave device, it is necessary to execute this sequence atomically to prevent register reads from being interrupted.
The i2c_sendrecv_t structure is defined as:
typedef struct { i2c_addr_t slave; /* slave address */ uint32_t send_len; /* length of send data in bytes */ uint32_t recv_len; /* length of receive data in bytes */ uint32_t stop; /* set stop when complete? */ } i2c_sendrecv_t;
If an error occurs, the command returns: