On Fri, Nov 14, 2008 at 08:55:38AM +0800, Greg KH wrote:
> On Thu, Nov 13, 2008 at 02:50:24PM +0800, Yu Zhao wrote:
> > On Fri, Nov 07, 2008 at 11:18:37AM +0800, Greg KH wrote:
> > > On Fri, Nov 07, 2008 at 11:01:29AM +0800, Zhao, Yu wrote:
> > > > Currently PCI subsystem has /sys/.../{vendor,device,...} bundled to the
> > > > main PCI device (I suppose this means the entries are created by
> > > > 'device_add')
> > > >
> > > > And after the PCI device is announced,
> > > > /sys/.../{config,resourceX,rom,vpd,iov,...} get created depending on if
> > > > these features are supported.
> > >
> > > And that's a bug. Let's not continue to make the same bug here as well.
> > >
> > > > Making dynamic entries tie to the main PCI device would require PCI
> > > > subsystem to allocate different 'bus_type' for the devices, right?
> > >
> > > No, it would just mean they need to be all added before the device is
> > > fully registered with the driver core.
> >
> > I looked into the PCI and driver core code again, but didn't figured out how
> > to do it.
> >
> > A 'pci_dev' is added by pci_bus_add_device() via device_add(), which creates
> > sysfs entries according to 'dev_attrs' in the 'pci_bus_type'. If we want those
> > dynamic entries to appear before the uevent is triggered, we have to bundle
> > them into the 'dev_attrs'. Is this right way for the dynamic entries? Or I
> > missed something?
>
> Yes, that is correct.
>
> Or you can add attributes before device_add() is called to the device,
> which is probably much easier to do, right?
>
> There are also "conditional" attributes, which get only displayed if
> some kind of condition is met, I think you want to use those.
The problem is the sysfs directory of the PCI device is created by the
kobject_add() in the device_add() as follows. And the static entries
bundled with the 'pci_bus_type' are created by the bus_add_device().
Between the kobject_add() and the kobject_uevent(), we don't have any
other choice to add the dynamic entries.
In device_add():
error = kobject_add(&dev->kobj, dev->kobj.parent, "%s", dev->bus_id);
...
error = bus_add_device(dev);
...
kobject_uevent(&dev->kobj, KOBJ_ADD);
So looks like the only way is to make the dynamic entries bundled with
the 'pci_bus_type', which means they would become static no matter the
device supports the entries (i.e. corresponding capabilities) or not.
Thanks,
Yu
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