linux-kernel - Re: [PATCH] Intel Management Engine Interface

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Message-ID: <20080814002305.GA7359@kroah.com>
Date:	Wed, 13 Aug 2008 17:23:05 -0700
From:	Greg KH <greg@...ah.com>
To:	Marcin Obara <marcin_obara@...rs.sourceforge.net>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] Intel Management Engine Interface

On Wed, Aug 13, 2008 at 08:48:19PM +0100, Marcin Obara wrote:
> 2008/8/13 Greg KH <greg@...ah.com>:
> >> GET_VERSION is called frequently
> >
> > Why?  Shouldn't it only be called once?
> Once per connection. But you can have many clients connecting.

Is that a real issue?

> >> With ioctl - only one file handle is used, and userspace client logic
> >> is simpler.
> >
> > But the kernel is messier and we are trying to not add any more ioctls
> > to it.  Especially for trivial things like the version number of the
> > hardware device.
> It's rather protocol version (=running software version) supported by
> hardware device.
> Hmmm, I just didn't know that there is something wrong with ioctls.

There always have been :)

> >> Normal flow looks like:
> >>
> >> open
> >> ioctl(GET_VERSION)
> >
> > Great, do an additional open/read/close here for the version, I think
> > you will find it pretty trivial to do :)
> Right, it's trivial.... but will make userspace source code messier and bigger.
> 
> Btw. I know we have powerful CPUs... but small wasting resources is
> still wasting resources... so we still need new CPUs :-).

So you keep your employer in business :)

Seriously, an ioctl for a hardware version number is total overkill
here.  Your other ioctls are also suspect, please repost with the
description of why they are all needed, with documentation about the
user/kernel interface you have created here.

thanks,

greg k-h
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