linux-kernel - RE: [char-misc-next 2/3] mei: adding sysfs fw

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Date:	Mon, 29 Jul 2013 23:08:52 +0000
From:	"Winkler, Tomas" <tomas.winkler@...el.com>
To:	Greg KH <gregkh@...uxfoundation.org>
CC:	"arnd@...db.de" <arnd@...db.de>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"Ovsyanikov, Natalia" <natalia.ovsyanikov@...el.com>
Subject: RE: [char-misc-next 2/3] mei: adding sysfs fw_status attribute


> >
> > >
> > > > > >
> > > > > >
> > > > > > > >
> > > > > > > > Just to make sure, is this what you're suggesting ?
> > > > > > > >
> > > > > > > > device->groups = mei_attr_groups
> > > > > > > > mei_misc_device.parent = device; ret =
> > > > > > > > misc_register(&mei_misc_device);
> > > > > > >
> > > > > > > Yes, that should work.  If not, please let me know, the code
> > > > > > > underwent some changes in 3.11-rc2.
> > > > > >
> > > > > > I don' t see the file being created.
> > > > > > Not sure if the  misc_register setup the parent sysfs as well.
> > > > >
> > > > > Oops, wait, the parent is already registered, that's not going
> > > > > to work, you want to create the files for the device itself that
> > > > > you are creating, so set the -
> > > > > >groups field for that device.
> > > > >
> > > > > sorry about that.
> > > >
> > > > So is this okay to go as  is?
> > >
> > > What is "this"?
> >
> > The intentions was to create the sysfs  on a  parent pci device, and
> > these are already created .
> 
> You can't create attributes on a device you do not "own", that will be racy
> and prone to cause big problems (your callback will not with the "right"
> device usually, as your parent might not "be" a pci device in the future...)
> 
> > The only reason I wanted do it here as this is true for any parent pci
> > device we support currently that registers with mei.
> >
> > Either this code ode is still confusing because  I'm  doing something
> > wrong here or  your mind Is set on fixing this particular user space
> > race issue.
> 
> Probably both...
> 
> Either way, you can't create sysfs files in a racy way, I'm going through the
> whole kernel tree to clean them all up, I'm not going to add new race
> conditions today that I need to fix up tomorrow, my patch count is high
> enough as it is :)

I understand your quest tough I'm asking you to throw some light on that
How do I add new device specific sysfs in non-race way if my entry point is the pci probe function.

Thanks
Tomas


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