Re: [Resend] pcibios_add_platform_entries usage

[Bjorn Helgaas <bhelgaas@google.com>]

[+cc Greg]

On Mon, Apr 14, 2014 at 11:03:42AM +0200, Sebastian Ott wrote:
> Hello Bjorn,
> 
> for pci on s390 we currently use pcibios_add_platform_entries to add
> some arch specific attributes to pdevs. This has 2 downsides - it will
> race with userspace which is triggered by udev events and expecting
> these attributes (but that's a theoretical issue). More important to
> me is that one cannot use attribute_groups with this. Both issues could
> be addressed by using pdev->dev.groups and let the driver core handle
> attribute creation.
> 
> So would it be ok if we set pdev->dev.groups in pcibios_add_device?
> (It should be since it's not used by pci common code which uses bus_type,
> dev_type, and class groups).

Hi Sebastian,

Sorry, I meant to respond to this earlier, but forgot.  This sounds
reasonable to me, but Greg can give you a much better answer than I can.

Documentation/driver-model/device.txt says the dev->groups pointer
should be set before calling device_register().  PCI calls
device_initialize() and device_add() instead of using device_register(),
and pcibios_add_device() looks like it happens at the right time:

    pci_scan_root_bus
      pci_scan_child_bus
        pci_scan_slot
          pci_scan_single_device
            pci_device_add
              device_initialize
              pcibios_add_device                # <---
              device_add
      pci_bus_add_devices
        pci_bus_add_device
          pci_create_sysfs_dev_files
            pcibios_add_platform_entries        # 8d4cd0833107 (benh)
          device_attach

I'm not sure why pci_create_sysfs_dev_files() is done later.  It seems
like that should be done before device_add() as well.  Maybe it's
because BARs might not be valid yet (that doesn't seem like a very good
excuse, but it's all I can think of).

I assume that if you change s390, you'll also change microblaze and
powerpc?  They look structurally similar to s390.

Bjorn