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SubjectRe: Write USB Device Driver entry not called
On Sat, 23 Oct 2004 07:12:56 +0530, eshwar <> wrote:
> I agree but the return value from the vfs_write should not be the -EBADF
> (Bad File descriptor) it might be -EACCES (premission denied)... Correct me
> if I am wrong...
> this can be code in fs/read_write.c vfs_write()
> if (!(file->f_mode & FMODE_WRITE))
> return -EACCES;

Wrong. You are confused between file perms & mode of access to files.
If you cannot open a file due to insufficient perms, then EACCESS is
what you get.
If you opened a file for reading, but you tried to write, the you get a EBADF.

Run the following code, after you create two files, 'foo' ( perms 0400
) and 'bar' ( 0700 ).

#include <fcntl.h>

int main()
int fd;

fd = open("foo",O_WRONLY);

if(fd < 0)
perror("Opening foo:");
close (fd);

fd = open("bar",O_RDONLY);

if(fd < 0)
perror("Opening bar: ");
else {
if(write(fd,'a',1) < 0)
perror("Write to bar failed: ");


Output would be:
Opening foo:: Permission denied
Write to bar failed: : Bad file descriptor
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