The write: foo_write in the struct file_operations struct is initializing
write , a pointer to a fn that takes the same params as foo_write, to
foo_write. Now when u say just foo_write in such an initialization , then
its a pointer to that fn.
Such pointers can be used just like any fn name in calling that fn .
So , u culd do
if struct file_operations sops; is an object of that struct , then u culd
do:
sops->write( fileptr, /* pointer to char */, sizeof(something),
/*offset*/);
and its as good as calling foo_write with respective arguments.
Narasimhamurthy Giri, Clemson University Computer Science Dept.
-------------------------------------------------------------------------------
Judge not lest ye be judged yourself.
-------------------------------------------------------------------------------
On Tue, 26 Mar 2002, Dan Erickson wrote:
>
> Hello,
> There is something that is highly confussing me in my quest to
> learn the linux kernel. Normally when you have a common prototype
> function, lets say, something small like a bitcounter. The bitcounter
> would need to take at least one argument, the prototype might look
> something like this....
>
> int bitcount(int integer);
>
> So now we have a function we can use in such a way as....
>
> int main()
> {
> int bitcount(int integer);
> int x = 5;
>
> printf("%d\n", bitcount(x));
> }
> What doesnt make sense to me is you have a prototype in a kernel
> driver such as ....
>
> static ssize_t foo_write(struct file *file, const char *buf,size_t count,
> loff_t *ppos)
> {
> /* Can't seek (pwrite) on this device */
> if (ppos != &file->f_pos)
> return -ESPIPE;
>
> if (count) {
> blah = blah1;
> return 1;
> }
>
> return 0;
>
>
> and then in the file_operations structure you would say something like
>
> static struct file_operations foo = {
> write: foo_write
> };
>
>
> Now my question is, what does the job of giving foo_write() its args?
>
> All other normal prototypes need to be given args,
> ie)
> int bitcount(int integer);
> has been given the argument "x"....
> so... bitcount(x)
> (from example at very top)
>
>
> I apologize for the amount of examples I have put in this post. I did it
> as I didnt quite know how to word my question properly.
>
> Thanks Alot
>
> -Dan Erickson-
> -ColdOneKnight@rogers.com-
>
> --
> Kernelnewbies: Help each other learn about the Linux kernel.
> Archive: http://mail.nl.linux.org/kernelnewbies/
> FAQ: http://kernelnewbies.org/faq/
>
>
--
Kernelnewbies: Help each other learn about the Linux kernel.
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