netdev - Re: [RFC][PATCH] Fix another namespace issue with devices assigned to classes

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Date:	Fri, 4 Jun 2010 10:34:07 +0200
From:	Kay Sievers <kay.sievers@...y.org>
To:	Johannes Berg <johannes@...solutions.net>
Cc:	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Greg KH <greg@...ah.com>, netdev <netdev@...r.kernel.org>
Subject: Re: [RFC][PATCH] Fix another namespace issue with devices assigned to 
	classes

On Fri, Jun 4, 2010 at 10:28, Johannes Berg <johannes@...solutions.net> wrote:
> On Fri, 2010-06-04 at 10:15 +0200, Kay Sievers wrote:
>> On Fri, Jun 4, 2010 at 08:54, Johannes Berg <johannes@...solutions.net> wrote:
>> > On Wed, 2010-06-02 at 17:53 -0700, Eric W. Biederman wrote:
>> >
>> >> Johannes this should fix your issue with mac80211_hwsim, where
>> >> the device symlink were not destroyed when the driver was removed.
>> >
>> > It does, thank you.
>> >
>> > FWIW, I'm happy changing hwsim too, but I don't think I quite understand
>> > what you're proposing in your other email so I'll leave it up to you
>> > since you now know what is causing the problem :)
>>
>> Assuming that hwsim is th parent of the network interface, it should
>> us a "struct bus_type" not a "struct class" for the subsystem it
>> assigns the devices to.
>
> It's all virtual, so yeah, I guess it is the parent? It currently
> creates a virtual struct device in the hwsim class and assigns that to
> the netdev parent indirectly via the wiphy or something like that.
>
>> Classes should not be used for anything completely simple, at best not
>> be used at all, they are just too simple. We never know about future
>> requirements, which usually all go wrong with the non-extendable class
>> logic.
>>
>> The difference in the code to switch from class to bus should be minimal.
>
> Does that mean cfg80211 (net/wireless/) should also not use a struct
> class? I'm not familiar with any of these details, mind helping me out?

Everything that might ever have a child device, or might ever need a
sysfs attribute gobal to the subsystem must convert to a bus.

Actually there is not much reason to ever use "struct class" today.
The layout for classes in /sys is not extendable like it is for buses
which put all devices in a devices/ subdir and have the main subsystem
directory to add custom things.

Kay
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