Embedded Linux development

* Re: Need help adding platform UIO devices to board
From: Nicholas Mc Guire @ 2012-11-28 19:03 UTC (permalink / raw)
  To: Alexander Varnin; +Cc: linux-embedded
In-Reply-To: <50B65DA3.9000707@mail.ru>

On Wed, 28 Nov 2012, Alexander Varnin wrote:

> Hello!
> I'm trying to add UIO device to my system to handle interrupt. But i'm
> facing following problem. Docs says, on reading device /dev/uio0 it will
> block until interrupt occurs. I've made simple program for test. It
> tries to write 1 to enable interrupts.
> 
>     #include <unistd.h>
>     #include <errno.h>
>     #include <fcntl.h>
>     #include <stdio.h>
> 
>     int main()
>     {
>         int fd;
>         char c = 1;
>         fd = open("/dev/uio0", O_RDONLY);
>         if (fd<0) {
>             printf("open error: %d\n", errno);
>              return 0;
>         }
>         printf("fd == %d\n", fd);
>         int res = write(fd, &c, 1);
>         if(res<0) {
>             printf("write error: %d\n", errno);
>         }
>         return 0;
>     }
>
open O_RDONLY and then write to it ?

return of 9 == EBADF

man 2 write

 EBADF  fd is not a valid file descriptor or is not open for writing.

hofrat 

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