Re: [PATCH] fix pktcdvd breakage from commit e105b8bfc769b0545b6f0f395179d1e43cbee822

Kay Sievers
2008-12-06T03:38:34Z

On Fri, 2008-12-05 at 03:57 +0100, Kay Sievers wrote:
> On Sun, Nov 30, 2008 at 16:56, Kay Sievers <kay.sievers@vrfy.org> wrote:
> > On Sun, Nov 30, 2008 at 15:52, Al Viro <viro@zeniv.linux.org.uk> wrote:
> >> On Sun, Nov 30, 2008 at 03:28:15PM +0100, Kay Sievers wrote:
> >>> > So we need to preserve the layout, with the easiest way probably being "add
> >>> > one more ktype and use kobject_init_and_add() instead of that device_create()".
> >>> > Sigh...
> >>>
> >>> What do you mean? We just need to replace the bogus "pd->pkt_dev" with
> >>> MKDEV(0, 0) and we are fine.
> >>
> >> Userland-visible change - right now cat /sys/class/pktcdvd/pktcdvd3/dev will
> >> give you dev_t of the block device in question.
> >
> > True, it's visible, but it's incorrect dead information which should
> > be removed. Subsystem != "block is defined as S_IFCHR, and there is no
> > such char device for pktcdvd. In fact the "dev" file of the pktcdvd
> > class device points in many cases to a USB device, which must be
> > fixed.
> >
> > The whole pktcdvd class is not used at all, besides for exporting a
> > few files. The "dev" file at the class device is just a bug, and the
> > MAJOR/MINOR uevent environment variables also. I doubt that there will
> > be any visible breakage in something that isn't already totally
> > broken. In short, I doubt, that anything that works today will stop
> > working if we remove the bugus "dev" file.
> >
> > This seem like the simple and correct fix for the issue with /sys/dev/
> > and the broken non-existing but exported pkcdvd char device:
> > - pd->dev = device_create(class_pktcdvd, NULL, pd->pkt_dev, NULL,
> > + pd->dev = device_create(class_pktcdvd, NULL, MKDEV(0, 0), NULL,
>
> Al, this bug still exists, right? Any objections to remove the dead char dev_t?

Here is a patch.

Thanks,
Kay

From: Kay Sievers <kay.sievers@vrfy.org>
Subject: pktcdvd: remove broken dev_t export of class devices

The pktcdvd created class devices only export some sysfs files,
but have no char dev_t registered in the driver.

At class device creation time they copy the dev_t value of the
block device to the char device, wich will register a new char
device in the driver core and userspace, with a conflicting dev_t
value.

In many cases the class devices dev_t just points to a random
USB device. This fixes the sysfs "duplicate entry" errors.

Cc: petero2@telia.com
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Kay Sievers <kay.sievers@vrfy.org>
---
pktcdvd.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

--- a/drivers/block/pktcdvd.c
+++ b/drivers/block/pktcdvd.c
@@ -302,7 +302,7 @@ static struct kobj_type kobj_pkt_type_wqueue = {
static void pkt_sysfs_dev_new(struct pktcdvd_device *pd)
{
if (class_pktcdvd) {
- pd->dev = device_create(class_pktcdvd, NULL, pd->pkt_dev, NULL,
+ pd->dev = device_create(class_pktcdvd, NULL, MKDEV(0, 0), NULL,
"%s", pd->name);
if (IS_ERR(pd->dev))
pd->dev = NULL;