Re: [PATCH 15/16 v6] PCI: document the SR-IOV sysfs entries

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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