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

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Date:	Wed, 13 Aug 2008 11:18:50 -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 08:16:02AM +0100, Marcin Obara wrote:
> 2008/8/13 Greg KH <greg@...ah.com>:
> > On Mon, Aug 11, 2008 at 09:23:01PM +0200, Marcin Obara wrote:
> >> +/* IOCTL commands */
> >> +#define IOCTL_HECI_GET_VERSION \
> >> +    _IOWR('H' , 0x0, struct heci_message_data)
> >
> > This can easily be a sysfs file, why not do that instead?
> >
> sysfs file would require additional file handle used by every userspace client.

So, is that really a great overhead?

> GET_VERSION is called frequently

Why?  Shouldn't it only be called once?

>, and sysfs file would create extra overhead.

Have you measured it?

> 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.

> 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 :)

thanks,

greg k-h
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