linux-kernel - Re: pktcdvd -> sysfs warning with 2.6.27

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Message-ID: <m3d4i32bs8.fsf@telia.com>
Date:	Tue, 14 Oct 2008 21:53:59 +0200
From:	Peter Osterlund <petero2@...ia.com>
To:	Kay Sievers <kay.sievers@...y.org>
Cc:	Greg KH <greg@...ah.com>, Nix <nix@...eri.org.uk>,
	linux-kernel@...r.kernel.org, a.zummo@...ertech.it
Subject: Re: pktcdvd -> sysfs warning with 2.6.27

Kay Sievers <kay.sievers@...y.org> writes:

> On Tue, 2008-10-14 at 10:38 +0200, Kay Sievers wrote:
>> On Tue, Oct 14, 2008 at 7:27 AM, Peter Osterlund <petero2@...ia.com> wrote:
>> > Greg KH <greg@...ah.com> writes:
>> >
>> >> Both of those should get "real" majors assigned to them.  It's not ok to
>> >> randomly go grabbing major:minor numbers like this for code that is in
>> >> mainline.
>> >
>> > It's not about random grabbing. It's about getting a dynamically
>> > assigned number. The pktcdvd driver once had static numbers, but at
>> > the time when the driver was merged into the mainline kernel, dynamic
>> > numbers were considered better. Therefore I changed the driver to use
>> > dynamic numbers.
>> 
>> The pktcdvd driver allocates a dynamic block major, which is fine. But
>> doesn't it use the same number, and now not allocated, for the char
>> devices it uses? That looks like something that needs to fixed, right?
>> 
>>   static void pkt_sysfs_dev_new(struct pktcdvd_device *pd)
>>   {
>>     if (class_pktcdvd) {
>>       pd->dev = device_create_drvdata(class_pktcdvd, NULL,
>>                                                 pd->pkt_dev, NULL,
>>                                                 "%s", pd->name);
>
> Something similar to this, with error checking, might be needed. It has
> two independent majors now in block and char:
>   $ grep pkt /proc/devices 
>   251 pktcdvd-char
>   252 pktcdvd

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.

Is it possible to create a custom directory in sysfs corresponding to
a block device? A directory /sys/block/pktcdvd0 is apparently created
automatically, but is it possible to extend that directory with driver
specific data?

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