Re: PCI driver code

[Parav Pandit <paravpandit@xxxxxxxxx>]

Any PCI driver which is written for PCI device, and using the latest PCI related APIs provides by the OS must define this structure properly.

 

This structure keeps the list of information such as

(a) Pointer to the pci_device_id table -

PCI device, vendor id for which OS should match the driver. (Previously driver iteself does the matching. Moving code to OS at one place reduces the overhead and code size of the drivers)

 

(b) function Pointer to the probe function which will be called by the OS when driver register the PCI Device using funciton pci_module_init() inside, module_init.

 

(c) name of the driver.

(d) function to remove the driver.

 

Parav

Ashok Sharma <aks6d@xxxxxxxxxxx> wrote:

Pl explain the following  structure declaration in PCI_driver code

static struct pci_driver foo_driver {
.name = ?foo?,
.probe = foo_probe,
.remove = foo_remove,
.id_table = foo_tbl,
};

consider me a novice only

Cheers
Ashok
Dinesh Ahuja <mdlinux7@xxxxxxxxxxx> wrote:

Hi Mulyadi,

> set_current_state(TASK_INTERRUPTIBLE);

>I think this is the problem. You set a running task
>into sleeping state, but didn't quickly follow it
with >re-scheduling function (that implicitly use wait
queue >too). What happen here was, your kernel thread
was >declared in sleeping state, time slice was
running >out, your thread was kicked out from CPU but
wasn't >runnable anymore.

This does not seems to be an issue as this line which
I have added to set the state of current process is
done in interruptible_sleep_time_out() function.
Removing this line does not solve problem and I still
get oops.

Internally, interruptible_sleep_time_out() invokes
schedule_timeout() {kernel/sched.c}. When I invoke
schedule_timeout directly, everything works fine. I
donot know what goes wrong when I try to invoke
interruptible_sleep_time_out().

Regards
Dinesh


Actually, you don't need it, because
interruptible_sleep_time_out do it
all for your.
--- Mulyadi Santosa wrote:

> Hi Dinesh...
>
> > Sorry for being late in replying back. I have used
> > schedule_timeout and it is working fine. But
> curious
> > to know what wrong is going on while using wait
> > queues.
> > I am working on kernel 2.4.20
> > Here is full code:
> [deleted]...
> > set_current_state(TASK_INTERRUPTIBLE);
>
> I think this is the problem. You set a running task
> into sleeping state,
> but didn't quickly follow it with re-scheduling
> function (that
> implicitly use wait queue too). What happen here
> was, your kernel
> thread was declared in sleeping state, time slice
> was running out, your
> thread was kicked out from CPU but wasn't runnable
> anymore.
>
> Actually, you don't need it, because
> interruptible_sleep_time_out do it
> all for your.
>
> I'll give another example how it is really done if
> you want to do it on
> very low level way. Take a look on
> wait_for_completion(). Comments are
> added inline:
> void wait_for_completion(struct completion *x)
> {
> spin_lock_irq(&x->wait.lock);
> if (!x->done) {
> // [Mulyadi]: declare a wait queue
> DECLARE_WAITQUEUE(wait, current);
>
> wait.flags |= WQ_FLAG_EXCLUSIVE;
> // [Mulyadi]: add to the wait queue first
> __add_wait_queue_tail(&x->wait,
> &wait);
> do {
> // [Mulyadi]: and then mark the current task as
> interruptible
>
> __set_current_state(TASK_UNINTERRUPTIBLE);
>
> spin_unlock_irq(&x->wait.lock);
> // [Mulyadi]: feel free to reschedule
> schedule();
>
> spin_lock_irq(&x->wait.lock);
> } while (!x->done);
> // [Mulyadi]: if you are done with it, remove the
> task from wait queue
> __remove_wait_queue(&x->wait,
> &wait);
> }
> x->done--;
> spin_unlock_irq(&x->wait.lock);
> }
>
> That way, the kernel knows that you're asking to be
> woken up when a
> signal is delivered, an event happens or simply
> because of timeout.
>
> So the conclusion is, as far as I know, declare a
> waitqueue, insert the
> task to waitqueue, and set the task state. Don't
> mess this order...
>
> regards,
>
> Mulyadi
>
>




__________________________________________________________
Yahoo! India Answers: Share what you know. Learn something new
http://in.answers.yahoo.com/

--
Kernelnewbies: Help each other learn about the Linux kernel.
Archive: http://mail.nl.linux.org/kernelnewbies/
FAQ: http://kernelnewbies.org/faq/

---

Now you can scan emails quickly with a reading pane. Get the new Yahoo! Mail.

---

Talk is cheap. Use Yahoo! Messenger to make PC-to-Phone calls.  Great rates starting at 1¢/min.