'read' system call fails for RAW devices

[ravikn76]

Hi All,

Trying to perform a read on a raw device on Red Hat Enterprise Linux AS release 4 Kernel 2.6.9-68.9 x86_64
the call to perror following the call to read() returns the following error message :-
Invalid argument.

The arguments passed to the read function seem valid.
Any help would be appreciated.

Thank you,
Ravi

[ravikn76]

Here is a testcode that I was using to test reading of raw devices on Linux.
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <errno.h>

int main(int argc, char *argv[])
{
int fd=-1;
int readSize;
char buffer[2048];
int ioFlag = 0;
mode_t mode = 0;
if(argc < 2)
{
printf("usage:test <fileName>\n");
exit(1);
}

if((fd = open(argv[1], ioFlag, mode)) < 0)
{
perror("file open failure:");
exit(1);
}

printf("fd = %d \n" , fd);
if(read(fd, (void *)buffer, 1024 ) < 0)
{
printf("errno = %d \n", errno);
perror("file read failure:");
exit(1);
}

close(fd);

return 0;
}


The program was compiled as follows:-
cc -o test test.c

The program was run as follows:-
./test /dev/raw/raw1

The output of the program is as follows:-
fd = 3
errno = 22
file read failure:: Invalid argument