On Thu, 11 Jul 2002, Shipman, Jeffrey E wrote:
> I'm not sure if this is the right place to ask this, but
> I have a question about ioctl(). I have a situation where
> I need to parse a file and build a hash table out of the
> information in user space. Then, I must pass that hash
> table into my module that's in kernel space. My question
> is: is ioctl() the way to go about this? I really don't
> know much about the function, but some people have mentioned
> it to me as the way to pass information between user and
> kernel space.
>
> If anyone has advice on if this is the way to go about it
> or how we could go about doing this would be greatly
> appreciated. Also, if anyone knows of any websites which
> may be helpful in this area, we'd appreciate that as
> well.
>
> Thanks.
>
> Jeff Shipman - CCD
> Sandia National Laboratories
> (505) 844-1158 / MS-1372
That's what ioctl() is/was designed for. In user-space, you have
int ioctl(fd, FUNCTION_NR, parameter);
... where fd is your open file-handle, FUNCTION_NR is whatever you want
to define a specific control for your device, and parameter is usually
a pointer to some parameters (like a buffer).
In the module, you have.
int any_name(struct inode *ip, struct file *fp, unsigned int command,
unsigned long arg);
'ip' and 'fp' will probably be ignored in your module.
'command' is your FUNCTION_NR, and 'arg' is your parameter.
You cast 'arg' to a pointer of your choice if the user-mode
code supplies a pointer.
The address (pointer) of your function goes into the
'struct file_operations' (7th member) that you pass a pointer
to when you initialize your device (register_xxxdev()).
The normal return code is 0. You return a -ERRNO if any errors
are encountered in your function.
Typically, you do:
switch(command)
{
case FIRST_FUNCTION:
....
break;
default:
return -ESPIPE; // Invalid stuff, lets you still test with
// standard text tools (od, hexdump, etc).
}
Cheers,
Dick Johnson
Penguin : Linux version 2.4.18 on an i686 machine (797.90 BogoMips).
Windows-2000/Professional isn't.
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
This archive was generated by hypermail 2b29 : Mon Jul 15 2002 - 22:00:20 EST