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

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Date:	Thu, 13 Nov 2008 16:55:38 -0800
From:	Greg KH <greg@...ah.com>
To:	Yu Zhao <yu.zhao@...el.com>
Cc:	"linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
	"achiang@...com" <achiang@...com>,
	"grundler@...isc-linux.org" <grundler@...isc-linux.org>,
	"mingo@...e.hu" <mingo@...e.hu>,
	"jbarnes@...tuousgeek.org" <jbarnes@...tuousgeek.org>,
	"matthew@....cx" <matthew@....cx>,
	"randy.dunlap@...cle.com" <randy.dunlap@...cle.com>,
	"rdreier@...co.com" <rdreier@...co.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"kvm@...r.kernel.org" <kvm@...r.kernel.org>,
	"virtualization@...ts.linux-foundation.org" 
	<virtualization@...ts.linux-foundation.org>
Subject: Re: [PATCH 15/16 v6] PCI: document the SR-IOV sysfs entries

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:
> > > Greg KH wrote:
> > >> On Wed, Nov 05, 2008 at 08:33:18PM -0800, Greg KH wrote:
> > >>> On Wed, Oct 22, 2008 at 04:45:15PM +0800, Yu Zhao wrote:
> > >>>>  Documentation/ABI/testing/sysfs-bus-pci |   33 
> > >>>> +++++++++++++++++++++++++++++++
> > >>>>  1 files changed, 33 insertions(+), 0 deletions(-)
> > >>>>
> > >>>> diff --git a/Documentation/ABI/testing/sysfs-bus-pci 
> > >>>> b/Documentation/ABI/testing/sysfs-bus-pci
> > >>>> index ceddcff..41cce8f 100644
> > >>>> --- a/Documentation/ABI/testing/sysfs-bus-pci
> > >>>> +++ b/Documentation/ABI/testing/sysfs-bus-pci
> > >>>> @@ -9,3 +9,36 @@ Description:
> > >>>>  		that some devices may have malformatted data.  If the
> > >>>>  		underlying VPD has a writable section then the
> > >>>>  		corresponding section of this file will be writable.
> > >>>> +
> > >>>> +What:		/sys/bus/pci/devices/.../iov/enable
> > >>> Are you sure this is still the correct location with your change to
> > >>> struct device?
> > >> Nevermind, this is correct.
> > >> But the bigger problem is that userspace doesn't know when these
> > >> attributes show up.  So tools like udev and HAL and others can't look
> > >> for them as they never get notified, and they don't even know if they
> > >> should be looking for them or not.
> > >> Is there any way to tie these attributes to the "main" pci device so
> > >> that they get created before the device is announced to the world?
> > >> Doing that would solve this issue.
> > >> thanks,
> > >> greg k-h
> > >
> > > 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.

thanks,

greg k-h
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