linux-kernel - RE: [PATCH v2 1/7] driver core: emit uevents when device is bound to a driver

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Date:   Fri, 29 Sep 2017 19:40:15 +0000
From:   "Ruhl, Michael J" <michael.j.ruhl@...el.com>
To:     "Williams, Dan J" <dan.j.williams@...el.com>,
        Dmitry Torokhov <dmitry.torokhov@...il.com>
CC:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Tejun Heo <htejun@...il.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Guenter Roeck <linux@...ck-us.net>
Subject: RE: [PATCH v2 1/7] driver core: emit uevents when device is bound
 to a driver

> -----Original Message-----
> From: dan.j.williams@...il.com [mailto:dan.j.williams@...il.com] On
> Behalf Of Dan Williams
> Sent: Friday, September 29, 2017 3:37 PM
> To: Dmitry Torokhov <dmitry.torokhov@...il.com>
> Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>; Tejun Heo
> <htejun@...il.com>; Linux Kernel Mailing List <linux-
> kernel@...r.kernel.org>; Guenter Roeck <linux@...ck-us.net>; Ruhl,
> Michael J <michael.j.ruhl@...el.com>
> Subject: Re: [PATCH v2 1/7] driver core: emit uevents when device is bound
> to a driver
> 
> On Wed, Jul 19, 2017 at 5:24 PM, Dmitry Torokhov
> <dmitry.torokhov@...il.com> wrote:
> > There are certain touch controllers that may come up in either normal
> > (application) or boot mode, depending on whether firmware/configuration
> is
> > corrupted when they are powered on. In boot mode the kernel does not
> create
> > input device instance (because it does not necessarily know the
> > characteristics of the input device in question).
> >
> > Another number of controllers does not store firmware in a non-volatile
> > memory, and they similarly need to have firmware loaded before input
> device
> > instance is created. There are also other types of devices with similar
> > behavior.
> >
> > There is a desire to be able to trigger firmware loading via udev, but it
> > has to happen only when driver is bound to a physical device (i2c or spi).
> > These udev actions can not use ADD events, as those happen too early, so
> we
> > are introducing BIND and UNBIND events that are emitted at the right
> > moment.
> >
> > Also, many drivers create additional driver-specific device attributes
> > when binding to the device, to provide userspace with additional controls.
> > The new events allow userspace to adjust these driver-specific attributes
> > without worrying that they are not there yet.
> >
> > Signed-off-by: Dmitry Torokhov <dmitry.torokhov@...il.com>
> 
> Hi Dmitry,
> 
> Mike (cc'd) reports a regression with this change:
> 
> ---
> 
> Previously, if I did:
> 
> # rmmod hfi1
> 
> The driver would be removed.
> 
> With 4.14.0-rc2+, when I remove the driver, the PCI bus is
> automatically re-probed and the driver re-loaded.
> 
> ---
> 
> A bisect points to commit 1455cf8dbfd0 "driver core: emit uevents when
> device is bound to a driver". I'm sending this because I have this
> mail in my archive, but I'll let Mike follow up with any other
> details.

My test environment is RedHat 7.3 GA + 4.14.0-rc2 kernel.

Blacklisting the driver keeps it from being autoloaded, but this didn't seem correct.

With the 4.13.x branch this did not occur

Thanks,

Mike