Re: [PATCH] fix pktcdvd breakage from commit e105b8bfc769b0545b6f0f395179d1e43cbee822

On Sun, Nov 30, 2008 at 13:19, Al Viro <viro@xxxxxxxxxxxxxxxxxx> wrote:
device_create() will create a symlink in /sys/dev/char unless
the class has ->dev_kobj cleared; pktcdvd uses it to populate the
/sys/class/pktcdvd/ with per-device subdirectories. While we do
want /sys/class/pktcdvd/pktcdvd[0-7]/dev to contain a device number,
we definitely do not want it to try and crap into /sys/dev/char; if
nothing else, device number is *block* one (and we don't want it
to crap into /sys/dev/block either - there such symlinks will be created
by add_disk() and they will point to /sys/block/pktcdvd[0-7]).

As it is, attempt to set the damn thing up will end up with
sysfs_add_one() barfing at duplicate entries and /sys/class/pktcdvd/pktcdvd*/*/
not created at all. The fix is trivial: clear ->dev_kobj in the class to
tell device_add() that no, we do *not* want these symlinks, TYVM...

FWIW, all traces containing pkt_setup_dev() on kerneloops.org appear
to be from that one. It had been around since 2.6.26; probably -stable
fodder...

Signed-off-by: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
---
diff --git a/drivers/block/pktcdvd.c b/drivers/block/pktcdvd.c
index f20bf35..79981f2 100644
--- a/drivers/block/pktcdvd.c
+++ b/drivers/block/pktcdvd.c
@@ -417,6 +417,7 @@ static int pkt_sysfs_init(void)
printk(DRIVER_NAME": failed to create class pktcdvd\n");
return ret;
}
+ class_pktcdvd->dev_kobj = NULL;
return 0;
}

I posted a fix for that weeks ago. But the pktcdvd maintainer stated,
that the char device nodes are not used for anything. So the whole use
of dev_t should be removed entirely. They just blindly claim the same
char dev_t the block devices use, and conflict with char devices from
other subsystems. Patching out the /sys/dev/class links fixes the
oops, but the underlying fundamental breakage will still exist.

Original mail here states:
"Maybe, but that character device would not be used for anything,
besides creating sub-directories in /sys/class/pktcdvd. The driver
implements a block device, not a character device."

http://lkml.org/lkml/2008/10/14/318

No idea why this never got fixed.

Thanks,
Kay
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