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

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Message-ID: <ac3eb2510811180849g7cb2f9d2n8603d02ca130b01c@mail.gmail.com>
Date:	Tue, 18 Nov 2008 17:49:05 +0100
From:	"Kay Sievers" <kay.sievers@...y.org>
To:	"Yu Zhao" <yu.zhao@...el.com>
Cc:	"Greg KH" <greg@...ah.com>,
	"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 Mon, Nov 17, 2008 at 09:09, Yu Zhao <yu.zhao@...el.com> wrote:
> On Fri, Nov 14, 2008 at 08:55:38AM +0800, Greg KH wrote:

>> 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.

There is device_add_attrs() which is just called between the calls you
mention above. Like Greg said, it can add groups, and groups have an
is_visible() callback, which can be used to conditionally create
attributes out of of predefined list.

Kay
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