On Mon, May 04, 2009 at 10:14:08PM +0530, arun c wrote:
> On Mon, May 4, 2009 at 9:40 PM, Greg KH <greg@xxxxxxxxx> wrote:
> > On Mon, May 04, 2009 at 09:16:54PM +0530, arun c wrote:
> >> On Mon, May 4, 2009 at 8:19 PM, Greg KH <greg@xxxxxxxxx> wrote:
> >> > On Mon, May 04, 2009 at 12:47:44PM +0530, arun c wrote:
> >> >> Hi all,
> >> >>
> >> >> I have a dual core system(I am running kernel 2.6.22, 2.6.16, or 2.6.27 ),
> >> >> where I can put a maximum of 8 similar PCI cards.
> >> >>
> >> >> So in my driver I register ('pci_register_driver()') with device ID and
> >> >> vender ID(same for all 8 cards).
> >> >>
> >> >> I need to access a global data from the probe functions. If there are
> >> >> 8 PCI devices detected probe function is called one after another?
> >> >>
> >> >> or is there any chance that they execute in parallel?
> >> >
> >> > Yes, in the future (and in some types of configurations today), it could
> >> > execute in parallel.
> >> >
> >> > Just use a lock to control access to your shared global data structure.
> >> >
> >> > But you might wish to revisit your usage of global data, why can't it be
> >> > a per-device field that is dynamically created for every individual
> >> > device? That would scale much better, right?
> >>
> >> I am using a character device interface to talk to my devices.
> >> only one character driver controlling all the PCI devices.
> >
> > Only 1? That seems like a design mistake :)
>
> But LDD3 says "but most devices that you will see are still organized on the
> one-major-one-driver principle", that's why I decided to use one major
> no for all the devices
One major is fine.
One minor isn't :)
> And my module init looks like this
>
> static int __init my_init_module(void)
> {
> struct cdev *cdev = &my_cdev; /* defined global */
> dev_t dev_id;
> int err;
>
> if (major) {
> dev_id = MKDEV(major, 0);
> err = register_chrdev_region(dev_id, 32, DEVICE_NAME);
> } else {
> err = alloc_chrdev_region(&dev_id, 0, 32, DEVICE_NAME);
> major = MAJOR(dev_id);
> }
>
> if (err)
> return err;
>
> cdev_init(cdev, &my_fops);
> cdev->owner = THIS_MODULE;
> cdev->ops = &my_fops;
> err = cdev_add(cdev, dev_id, 32);
> if (err)
> return err;
> err = pci_register_driver(&my_pci_driver);
> if (err)
> goto clean_cdev;
>
> return 0;
>
> clean_cdev:
> cdev_del(cdev);
> unregister_chrdev_region(dev_id, 32);
> return err;
>
> Are you saying that this is wrong?, and I should use only
> pci_register_driver() in my init module and use individual
> character drivers for all the pci devices probed?
Ok, no, this makes a bit more sense, although you are limiting yourself
to 32 total devices in the system.
So yes, you will need a lock to protect you giving out your minor
numbers to individual devices.
Just curious, what type of device is this that you are creating a new
major device number for? I thought we pretty much cover all types of
devices with different subsystems in the kernel today.
thanks,
greg k-h
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