linux-kernel - Re: [PATCH] Allow userspace to request device probing even if defer_all

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Message-ID: <20170104194214.GB25268@kroah.com>
Date:   Wed, 4 Jan 2017 20:42:14 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     Matthew Garrett <mjg59@...eos.com>
Cc:     Kees Cook <keescook@...omium.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        kernel-hardening@...ts.openwall.com
Subject: Re: [PATCH] Allow userspace to request device probing even if
 defer_all_probes is true

On Wed, Jan 04, 2017 at 12:11:49PM -0600, Matthew Garrett wrote:
> On Wed, Jan 4, 2017 at 3:13 AM, Greg Kroah-Hartman
> <gregkh@...uxfoundation.org> wrote:
> >> Add a force_probe sysfs node to each device, which if written will
> >> trigger a probe even if defer_all_probes is currently true.
> >
> > Why not just manually trigger the bind of the device?  I don't
> > understand the problem here that is being addressed, nor do I understand
> > how this would be used.  More explaination please.
> 
> Userspace doesn't know the order that the kernel will use when
> attempting to bind drivers, so punting binding out to userspace may
> result in different behaviour.

How can the order in which drivers are bound result in different
behavior?

> The kernel already has the code to do this, so we should just reuse
> it.

That's fine, but I don't understand the problem you are trying to solve,
please explain better.  What am I missing here?

thanks,

greg k-h