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/*                                                                                                                                                                                                                                                                                 
 * Sample application that makes use of the SPIDEV interface                                                                                                                                                                                                                       
 * to access an SPI slave device. Specifically, this sample                                                                                                                                                                                                                        
 * reads a Device ID of a JEDEC-compliant SPI Flash device.                                                                                                                                                                                                                        
 */                                                                                                                                                                                                                                                                                
                                                                                                                                                                                                                                                                                   
#include <stdio.h>                                                                                                                                                                                                                                                                 
#include <sys/types.h>                                                                                                                                                                                                                                                             
#include <sys/stat.h>                                                                                                                                                                                                                                                              
#include <fcntl.h>                                                                                                                                                                                                                                                                 
#include <unistd.h>                                                                                                                                                                                                                                                                
#include <sys/ioctl.h>                                                                                                                                                                                                                                                             
#include <linux/types.h>                                                                                                                                                                                                                                                           
#include <linux/spi/spidev.h>                                                                                                                                                                                                                                                      
#include <stdint.h>                                                                                                                                                                                                                                                                
#include <stdio.h>                                                                                                                                                                                                                                                                 
#include <string.h>                                                                                                                                                                                                                                                                
#include <errno.h>                                                                                                                                                                                                                                                                 
                                                                                                                                                                                                                                                                                   
int main(int argc, char **argv)                                                                                                                                                                                                                                                    
{                                                                                                                                                                                                                                                                                  
        char *name;                                                                                                                                                                                                                                                                
        int fd;                                                                                                                                                                                                                                                                    
        struct spi_ioc_transfer xfer[2];                                                                                                                                                                                                                                           
        unsigned char buf[32], *bp;                                                                                                                                                                                                                                                
        int len, status;                                                                                                                                                                                                                                                           
                                                                                                                                                                                                                                                                                   
        name = argv[1];                                                                                                                                                                                                                                                            
        fd = open(name, O_RDWR);                                                                                                                                                                                                                                                   
        if (fd < 0) {                                                                                                                                                                                                                                                              
                perror("open");                                                                                                                                                                                                                                                    
                return 1;                                                                                                                                                                                                                                                          
        }                                                                                                                                                                                                                                                                          
                                                                                                                                                                                                                                                                                   
        memset(xfer, 0, sizeof xfer);                                                                                                                                                                                                                                              
        memset(buf, 0, sizeof buf);                                                                                                                                                                                                                                                
        len = sizeof buf;                                                                                                                                                                                                                                                          
                                                                                                                                                                                                                                                                                   
        /*                                                                                                                                                                                                                                                                         
         * Send a GetID command                                                                                                                                                                                                                                                    
         */                                                                                                                                                                                                                                                                        
        buf[0] = 0x9f;                                                                                                                                                                                                                                                             
        len = 6;                                                                                                                                                                                                                                                                   
        xfer[0].tx_buf = (unsigned long)buf;                                                                                                                                                                                                                                       
        xfer[0].len = 1;                                                                                                                                                                                                                                                           
                                                                                                                                                                                                                                                                                   
        xfer[1].rx_buf = (unsigned long) buf;                                                                                                                                                                                                                                      
        xfer[1].len = 6;                                                                                                                                                                                                                                                           
                                                                                                                                                                                                                                                                                   
        status = ioctl(fd, SPI_IOC_MESSAGE(2), xfer);                                                                                                                                                                                                                              
        if (status < 0) {                                                                                                                                                                                                                                                          
                perror("SPI_IOC_MESSAGE");                                                                                                                                                                                                                                         
                return -1;                                                                                                                                                                                                                                                         
        }                                                                                                                                                                                                                                                                          
                                                                                                                                                                                                                                                                                   
        printf("response(%d): ", status);                                                                                                                                                                                                                                          
        for (bp = buf; len; len--)                                                                                                                                                                                                                                                 
                printf("%02x ", *bp++);                                                                                                                                                                                                                                            
        printf("\n");                                                                                                                                                                                                                                                              
                                                                                                                                                                                                                                                                                   
        return 0;                                                                                                                                                                                                                                                                  
}