linux-kernel - Re: [PATCH 32/36] driver core: Introduce device

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Date:	Tue, 5 Dec 2006 21:58:43 -0800
From:	Greg KH <gregkh@...e.de>
To:	Marcel Holtmann <marcel@...tmann.org>
Cc:	Greg KH <greg@...ah.com>, linux-kernel@...r.kernel.org,
	Cornelia Huck <cornelia.huck@...ibm.com>
Subject: Re: [PATCH 32/36] driver core: Introduce device_move(): move a device to a new parent.

On Tue, Dec 05, 2006 at 04:26:11PM +0100, Marcel Holtmann wrote:
> Hi Greg,
> 
> > > > > > Provide a function device_move() to move a device to a new parent device. Add
> > > > > > auxilliary functions kobject_move() and sysfs_move_dir().
> > > > > > kobject_move() generates a new uevent of type KOBJ_MOVE, containing the
> > > > > > previous path (DEVPATH_OLD) in addition to the usual values. For this, a new
> > > > > > interface kobject_uevent_env() is created that allows to add further
> > > > > > environmental data to the uevent at the kobject layer.
> > > > > 
> > > > > has this one been tested? I don't get it working. I always get an EINVAL
> > > > > when trying to move the TTY device of a Bluetooth RFCOMM link around.
> > > > 
> > > > I relied on Cornelia to test this.  I think some s390 patches depend on
> > > > this change, right?
> > > 
> > > my pre-condition is that the TTY device has no parent and then we move
> > > it to a Bluetooth ACL link as child. This however is not working or the
> > > TTY change to use device instead of class_device has broken something.
> > 
> > Hm, I don't think the class_device stuff has broken anything, but if you
> > think so, please let me know.
> 
> I was checking why device_move() fails and it seems that the check for
> is_registered is the problem here.
> 
>         if (!device_is_registered(dev)) {
>                 error = -EINVAL;
>                 goto out;
>         }
> 
> The ACL link has been attached to the Bluetooth bus, but for some reason
> it still thinks that it is unregistered. Is this check really needed. I
> think it should be possible to also move devices that are not part of a
> bus, yet. And removing that check makes it work for me.
> 
> And btw. I can't see any s390 patches that are using device_move() at
> the moment.
> 
> > > > > And shouldn't device_move(dev, NULL) re-attach it to the virtual device
> > > > > tree instead of failing?
> > > > 
> > > > Yes, that would be good to have.
> > > 
> > > Cornelia, please fix this, because otherwise we can't detach a device
> > > from its parent. Storing the current virtual parent looks racy to me.
> > 
> > You can always restore the previous "virtual" parent from the
> > information given to you in the device itself.  That is what the code
> > does when it first registers the device.
> > 
> > And yes, I too think it should be fixed.
> 
> My knowledge of the driver model is still limited. Can you fix that
> quickly. This is really needed.

As Cornelia wrote this portion of code, I will wait a bit to recieve a
patch...

Cornelia?

thanks,

greg k-h
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