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

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Message-ID: <alpine.LFD.1.10.0812092252590.12990@quad.localdomain>
Date:	Tue, 9 Dec 2008 22:57:26 +0100 (CET)
From:	Peter Osterlund <petero2@...ia.com>
To:	Kay Sievers <kay.sievers@...y.org>
cc:	Al Viro <viro@...iv.linux.org.uk>,
	Linus Torvalds <torvalds@...ux-foundation.org>, gregkh@...e.de,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] fix pktcdvd breakage from commit
 e105b8bfc769b0545b6f0f395179d1e43cbee822

On Sat, 6 Dec 2008, Kay Sievers wrote:

> On Fri, 2008-12-05 at 03:57 +0100, Kay Sievers wrote:
>> On Sun, Nov 30, 2008 at 16:56, Kay Sievers <kay.sievers@...y.org> wrote:
>>> On Sun, Nov 30, 2008 at 15:52, Al Viro <viro@...iv.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.

I can confirm that this patch doesn't seem to cause any negative side 
effects on either pktsetup or pktcdvd, which are the only two user space 
programs I know of that care about the pktcdvd driver.

Acked-by: Peter Osterlund <petero2@...ia.com>


> Thanks,
> Kay
>
>
> From: Kay Sievers <kay.sievers@...y.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@...ia.com
> Cc: Al Viro <viro@...iv.linux.org.uk>
> Signed-off-by: Kay Sievers <kay.sievers@...y.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;

-- 
Peter Osterlund - petero2@...ia.com
http://web.telia.com/~u89404340
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