linux-kernel - Re: [PATCH] pci: keep pci device resource name pointer right.

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Date:	Sat, 18 Apr 2009 12:23:14 -0700
From:	Greg KH <gregkh@...e.de>
To:	Yinghai Lu <yinghai@...nel.org>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Jesse Barnes <jbarnes@...tuousgeek.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	"H. Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...e.hu>,
	Thomas Gleixner <tglx@...utronix.de>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	linux-pci@...r.kernel.org
Subject: Re: [PATCH] pci: keep pci device resource name pointer right.

On Sat, Apr 18, 2009 at 12:19:21PM -0700, Yinghai Lu wrote:
> Linus Torvalds wrote:
> > 
> > On Fri, 17 Apr 2009, Yinghai Lu wrote:
> >> it turns that we need to reget res->name because dev->dev.kobj name is changed
> >> after device_add.
> > 
> > Can we not make the rule be that the name should just be set before?
> > 
> > IOW, there is something else broken, I think. Rather than put this ugly 
> > band-aid, why now make sure that whoever had that broken name fixes it?
> > 
> 
> driver core guys are enforcing to use dev_name(device) instead of referring it.

By "enforcing" you now mean, "there is no other way" :)

> for pci code:
> 
> via acpi_pci_root_driver.ops.add (aka acpi_pci_root_add) ==>
> pci_acpi_scan_root is used to scan pci bus/device, and at the same we
> read the resource for pci_dev  at this point still need to use
> bus->devices to go over all pci_devices if needed.
> in the pci_read_bases, we have res->name = pci_name(pci_dev); pci_name
> is calling dev_name.
> 
> later via acpi_pci_root_driver.ops.start (aka acpi_pci_root_start) ==>
> pci_bus_add_device to add all pci_dev in kobj tree.
> 
> pci_bus_add_device will call device_add. 
> 
> actually in device_add
> 
>         /* first, register with generic layer. */
>         error = kobject_add(&dev->kobj, dev->kobj.parent, "%s", dev_name(dev));
>         if (error)
>                 goto Error;
> 
> will get one new name for that kobj, old name is freed.
> 
> Will try to make kobject_add more smart to reuse the old one.

I don't understand the problem here, how are you going to change the
kobject core?  Is this just because you aren't getting a name for the
resource?  If so, why would the driver core care about this?

confused,

greg k-h
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