linux-kernel - Re: [RFC] bind/unbind uevent

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Message-ID: <20101207183305.GA21802@suse.de>
Date:	Tue, 7 Dec 2010 10:33:05 -0800
From:	Greg KH <gregkh@...e.de>
To:	Sebastian Ott <sebott@...ux.vnet.ibm.com>
Cc:	Kay Sievers <kay.sievers@...y.org>, linux-kernel@...r.kernel.org
Subject: Re: [RFC] bind/unbind uevent

On Tue, Dec 07, 2010 at 06:29:37PM +0100, Sebastian Ott wrote:
> 
> On Tue, 7 Dec 2010, Greg KH wrote:
> > On Tue, Dec 07, 2010 at 05:18:27PM +0100, Sebastian Ott wrote:
> > > Hi,
> > > 
> > > There is currently no generic trigger for userspace to know when a driver
> > > is bound to a device.
> > 
> > Not true at all, you get one when a device is attached to a bus.  What's
> > wrong with that notification?
> we get a KOBJ_ADD if a device is attached to a bus, but this does not
> imply that a device driver is bound to this device

You can get that information from that uevent, it's all there for you to
listen to.

> > > Such a trigger may be required in cases where setup
> > > steps must be performed in userspace after the device is bound, e.g.
> > > because the driver adds sysfs attributes in its probe function.
> > 
> > A driver should not add sysfs attributes in its probe function as that
> > is racy as you have noticed.  Add the attributes in the bus functions
> > for that driver and it should be fine.
> sry..I was not clear on this one. I was talking driver specific
> attributes per device.

No, I understand.

> So I'm searching for a trigger when these attributes are created, or
> in other words when the device is useable, which I think translates to
> when a driver is bound to this device.

Again, KOBJ_ADD is the correct one.

If your driver is creating sysfs attributes on its own, that's a bug and
should be fixed.

thanks,

greg k-h
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