Re: [PARPORT] simple driver

From: Aditya Mittal (
Date: Wed Apr 11 2001 - 16:08:48 EDT

  • Next message: Philip Blundell: "Re: [PARPORT] simple driver"

    On Wed, 11 Apr 2001, Philip Blundell wrote:

    > >read_write_t scope_write(struct inode *inode, struct file *filp,
    > > const char *buf, count_t count)
    > >{
    > What version of the kernel are you using? That kind of write() signature
    > hasn't been appropriate since 2.0 or so. Also:

    i am using kernel 2.2.14-12

    > > copy_from_user(kbuf, buf, count);
    > This function returns an error flag; you ought to check for success. Also:

    i checked errno in the program that is using the driver, the code is

         int fd;
         char *buf;
         int ret;
         extern int errno;
         printf("enter data\n");
         buf=(char *)malloc(10*sizeof(char));
         if (fd>0){
              printf("string is %s, length = %d\n",buf,strlen(buf));
              if(ret <= 0)
                   printf("error!! %d %d\n",ret,errno);
              printf("driver not loaded! \n");

    the output is ...

    enter data
    kmalloc: Size (3271436788) too large
    string is adit, length = 4
    error!! -1 12
    an errno of 12 according to asm/errno.h is ENOMEM (out of memory)
    but that seems unlikely...

    > > outb(*(ptr++),port);
    > It would probably be better to use the parport functions rather than
    > attacking the bare metal directly, though that's a matter of choice.

    can you please elaborate a bit as i am a total newbie to writing device
    drivers :)

    can you please point to some resource which explains how to use these
    parport functions and how to build drivers out of these?


    -- aditya

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