linux-kernel - Re: [PATCH] fix pktcdvd breakage from commit e105b8bfc769b0545b6f0f395179d1e43cbee822

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Date:	Sun, 30 Nov 2008 14:57:14 +0100
From:	"Kay Sievers" <kay.sievers@...y.org>
To:	"Al Viro" <viro@...iv.linux.org.uk>
Cc:	"Linus Torvalds" <torvalds@...ux-foundation.org>, gregkh@...e.de,
	petero2@...ia.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] fix pktcdvd breakage from commit e105b8bfc769b0545b6f0f395179d1e43cbee822

On Sun, Nov 30, 2008 at 14:50, Al Viro <viro@...iv.linux.org.uk> wrote:
> On Sun, Nov 30, 2008 at 02:44:24PM +0100, Kay Sievers wrote:
>
>> >> Which part of the above constitutes a creation of char device node?
>> >
>> > Wait a minute...  Are you saying that something in userland ends up
>> > seeing that sucker, noticing .../dev and proceeding to do mknod?
>>
>> Sure, it does mkod, as the kernel says it should. But that does not
>> cause any real problem.
>
> "It" being udev, presumably?

Yes, udev, mdev, and a few other tools people use to populate /dev
from the kernel supplied device information.

> What a mess...  How does drivers/usb/core/devio.c avoid essentially the same
> problem?

It's a special case, where two "struct device" have the same dev_t,
but they both point to and handle the same device, so it's fine. The
usb_device class is deprecated, no recent distro uses it, and will be
removed some day.

The /sys/dev/ is handled properly by doing:
  usb_classdev_class->dev_kobj = NULL;

Kay
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